I do back up to my computer. But not every day, like I can with an SD card. I've never had an SD card fail on me, and having one has saved me when my Note 4 memory died. Having one makes it easier to transfer data between phones.
I've already given up removable batteries and headphone jacks. Why do I have to give up every single feature that used to be considered a basic necessity? Why should I spend so much money upfront for storage that I may not need, when I could easily expand it with an SD card if I need for much cheaper down the line?
I already tried a phone without an SD card slot and look where it got me. Installing the custom ROM was a pain. Transferring my data was a pain. The motherboard died with no warning, and now I've lost 2 months worth of data. I'm not doing this again.