While I generally agree with you about sd cards - they are such a kludge - I can't believe that you don't have the imagination to understand why some people want more local storage.
Some people don't want to rely on cloud services; data connections are nearly ubiquitous, but there are still dead spots out there (like my house, for example, where I need to walk about a quarter mile to get a good enough signal to make a phone call on any network. Thankfully, there are things like network extenders.) Some people just want a smartphone to be a phone and an internet access device and a way to access their own content locally without a company like Google or Apple knowing their music interests, etc. Some people have capped internet access at home as well as on their mobile plans, so uploading a lot of music and accessing movies can be expensive.
It's good that there are options out there with sd cards, but it's also a little weird that android models don't come with a wider range of local storage options, like iPhones do, so somebody who wants more local storage can choose to get a phone with 64 or 128 GB rather than a one or two size fits all model that most android models are restricted to, if they are not going to allow removable storage.