I totally agree. However, that is how these, free apps make their money. They push payware on you and get people who aren't paying attention to change settings such as their default search engine. A search engine isn't something you install (unless you're installing a toolbar or something related to it), it is simply a website.
I don't know what the solution is. Unlike you, I'm not willing to pay for most of my apps. I guess I'd rather just be vigilant when installing and make sure I don't accidentally uncheck everything. Actually, while I do maintain a Windows system or two in my house and I have to run one for work, I am primarily a Linux user. The Linux installers for most of these apps don't try to play these tricks which is refreshing. However, Linux isn't practical for someone who isn't an IT professional. I feel perfectly comfortable at the command line and I can troubleshoot weird bugs and get hardware working that doesn't work by default when I install a distribution.
If I didn't know my way around Linux, I would have been in trouble more times than I can count. I wish that they could come out with a simple distribution with minimal bugs that is very easy to use. I mean ubuntu or mint Linux is probably about as close as you can get to this (I prefer xubuntu to use the xfce4 window manager or kubuntu for KDE 4). It's default Window manager (unity) will never be for me, but not everyone hates it. There are also hundreds of other Linux distributions. Also, while Linux has support for a handful of games, and usually comes packaged with LibreOffice, the conversion of LibreOffice to MS office documents and vice versa is hardly ever perfect. It is possible to get MS Office working in Linux, there have been commercial apps like CrossOver Office that help with this, but they aren't perfect. I think CrossOver office died because it just had too many bugs and people weren't willing to pay money for a product like that. They should have kept it free and made it a stable product before going commercial, but the same issue would come up every time the version of Office changed..