I don’t, and I don’t recall ever seeing anyone else ever microwave something on anything other than full power or defrost. Do you use any of the other settings?
The only buttons I ever press is the 30-second quick start and the stop button. I have no idea what any of the other buttons do.
I can’t even remember the last time I used defrost.
Same here. There seem to be all sorts of possible settings, but I’ve never used them.
My microwave’s power setting is in 10 increments, 1-10, and I use most of them. Power Level is the first button I hit, before entering the time. I never before thought this was unusual.
My oven only has two settings, full power and defrost. Besides those there’s the dial to set the time and that’s it.
I’ve started using lower power settings than max to steam vegetables for cooking. (I like my carrots mushy.) 3 minutes at max, then stir, then 10 minutes at power level 3, stir again, 10 minutes at power level four. Then they’re ready. 
I actually never use defrost.
I do use the 50% and 80% power settings when cooking rice and pasta.
Potatoes get cooked at a (1-9 settings) power level 4.
Popcorn has its own button! 
Mine has various ‘Reheat’ settings, which, along with the ‘Popcorn’ option, are actually the ones I use most often. I think I’ve only used defrost a half a dozen times in ten years. I’ve used full Warp Factor 10 power quite a bit more than that, however.
And what’s that popcorn button for? 
Nearly every microwave popcorn I’ve ever used has said NOT to use the popcorn setting.
Our microwave oven is a Panasonic Genius II (similar to the one shown here) from the early 1980s. It’s got a table on the front listing the various things that can be cooked automatically using the built-in programs.
To start it normally, you have to select among 5 power levels, then select the duration. We frequently use levels 5 (max), 4 and 3.
I mainly use full power or defrost, but at least once a week I’ll set the exact power level I want. Usually it’s for something that’s difficult to defrost or something I want cooked a particular way.
I use the power levels all the time, especially when reheating foods. I’ll double the time and put the power at 50%, so things heat more evenly.
We also use the Beverage button, which is handy to get a hot beverage that isn’t going to explode when you put the sugar in.
I use the beverage button, the popcorn button, and power level 3 (for reheating pizza or any bakery item, including warming up cookies) in addition to full power.
Those plus the “quickset” button.
I do that with the baby’s food. I’m never sure whether 1 minute at 50% is really any different from 30 seconds at full power, though.
I’ve also had good luck with the Potato button, at least when I’m cooking potatoes.
I use the “Reheat” button all the time. Much more control than full power.
3 minutes on power 2 defrosts two boned and skinned chicken thighs to perfect dicing firmness. I add cumin, garlic, cayenne, and black pepper. I then cook the chicken and make awesome tacos.
Ditto. Additionally, I use lower setting when making rice or oatmeal (full power initially, and then lower power to cook).