The answer is..... it depends.

If all I am using the hotel room for is to come in, go to sleep, wake up, shower, change, and head out then I don't care if I'm upgraded or not.

If however I'm going to be working in the evening or staying a few days, then having a bit more room to spread out, or have a separate living area where you can relax without having to use the bed all the time, or even having a little kitchen can be really nice.

It's like saying the only purpose of a car is to be able to drive from point a to point b, so why doesn't everybody just rent the cheapest compact? For some people that's fine, but for some others, they want something a bit better.

Many hotels offer both kinds of rooms because there are people who are happy in the shoe box, and others who want the divided boot box.