Hi Everyone,
I have read this good post and some of the good replies to it. Here are my thoughts on this as well.
The answer is yes people could use their phone and phone provider's carrier for phone and home internet service because I have been doing this since last year. Keep in mind, I am one person with a lot of internet connected stuff.
But, there are various things to consider depending on what you want or need the internet for.
I am a power user that uses around 100 gb or more per month and I have 2 computers, a desktop and laptop, various Google Home devices, various video streaming devices including a Roku streaming stick plus, etc...
I think it is very important to have a good reliable phone unlimited data plan. But, It is in my humble opinion IMHO very difficult to find a truly unlimited phone provider plan at a reasonable cost especially for one or two people. Most phone providers are misleading people claiming unlimited data plan when in fact, as has been stated, most plans only have a certain small amount of high speed data at 4G or 5G then the speed drops to 3G or 2G or even less. As far as I'm concerned, 2G speed or less is unusable. Anything less than 25 GB per month can easily and quickly be used up especially if you are streaming video.
There are a couple options for using your phone provider for internet service that obviously depends on the phone provider plan and your phone hardware, simply turn on the phone's hotspot or use USB tethering. Depending on the phone provider, you may not have hotspot or USB tethering available, then you'll have to find another phone provider that supports it. And, the phone provider may limit hotspot or USB tethering in various ways like only one hotspot connection and limited speed to something like 5 Mbps.
In order to really use a phone provider as a home or business internet, you will probably need and want to connect it to a fast dual band router that supports connecting to a WiFi hotspot or wireless router using repeater mode, bridge mode, wisp mode, etc... and or USB tethering and not all routers support these connectivity options. I got an Asus ac1900 router that does support these connectivity options and works really well. Most open source routers will also support these connectivity options. I prefer using the USB tethering because it keeps the phone charged and it's easy to set up a private secure network for everything else to connect with, but then the phone is not portable anymore because of the USB cable to the router. If I use the phone's WiFi hotspot, then the phone stays portable, but my Asus router must be in repeater mode making network management a little more difficult. Some routers like open source routers have a wisp mode for connecting to other WiFi routers or hotspots making that easy to setup and manage.
I really like having a portable internet that is not affected by power outages like cable or fiber or satellite internet is, I can take it with me to wherever I go, etc...
I decided that it would be better for me to get another Android phone using another phone provider with some data or unlimited data as my carry around phone and just leave the one Android phone with unlimited everything connected at home. This is advantageous because I have a backup phone number and provider if something happens to my one phone and or it's service.
Although I would love to have the best Android phones and fastest internet options, I currently cannot afford that. I have two relatively low cost Android phones, a Nokia 6 and a Moto E6.
So, I found Visible phone provider running on the Verizon network for $40 per month with truly unlimited everything including data which if you use their cool and great Party Pay plan is now only $25 per month. But, its hotspot or USB tethering is limited to 5 Mbps and only one hotspot connection which using a good WiFi router allows me to connect everything to my home network through the one hotspot or USB tethering connection. I have been able to use Netflix and other streaming video services without issues using the 5 GHz band or Ethernet while doing other computer related activities. Of course that's not 4K or higher video streaming quality or fast downloading and I don't have other multiple users doing gaming or video streaming, but it works fairly well until I can find a better alternative.
I have been trying many other lower cost prepaid phone providers using one of the phone's as my carry around phone for typical phone stuff like unlimited talk, text, and some data or unlimited data. I am looking for another reasonable unlimited high speed data plan provider for that phone as well.
At the moment, I have 2 phones and 2 phone providers with unlimited calls, text, and one with unlimited 4G data the other with some high speed data then unlimited lower speed data all for $40 us per month or less.
FYI - T-Mobile does have a great high speed home internet option for $50 a month, no phone service, just internet service, but it is not yet available everywhere.
I hope this helps some people. Everyone have a great day and night.