Just like said before, some use for comfort (can be for the feel, anxiety, depression, thrill, etc.), but some use to pee, and or mess on purpose, some can not control their body due to medical issues, some use or just wear for sexual purposes.
I wouldn't limit good quality to just one brand. Megamax is really good, but also trest, rearz, Little For Big, and more. You would have to experiment on you own to see what fits you. Do you want plain diapers, or printed. With printed, there are lots of patterns to choose from to suit you. You have several choices too! Plastic backed, tape style tabs, hook and loop tabs. To throw a curve ball, you can also use boosters to make the asborncy level go up, and make the diaper thicker. That's just on the disposable side for now. I'm sure there will probably be more answers.
I do not know much on the cloth side, but I'm sure there are members here that could help. But with cloth, you can get plastic pants to go over them (which can also go over disposables) to help preventing leakage. Those come in a wide variety of colors, and styles as well. There are several styles of cloth as well. Can kick it old school with a pin, there are snaps and velcros i believe. Could be wrong. If so, I'm sorry.
Now to your question, alot could be same answers, different, or even a mix. For me, well there is a satisfying feeling usually non- sexual of wetting myself. It feels helpless, but exciting at the same time. The thought that "hey, I'm potty trained and I'm wetting myself", makes it feel more risqué, not trying to get caught.
With my job, i can be diapered while working most of the time. I'm an OTR (Over The Road) truck driver. Trying to be hydrated and keep working is hard. Being such a large vehicle, I just can't pull into any gas station or rest areas (some states in the US has a car only rest area). I have to wait until i can find somewhere if not diapered which sometimes can be over 50-100 miles away. When that urge hits, can't always hold it for 45 minutes to an hour and half. So it helps.
But simplified, it just feels great. Just try and perceive it your way. Take your feeling in consideration and have fun. I would recommend trying samples first to see what fits better, feels better, and what capacity level you want. If you aren't sure about size or right on the border line, one thing i read up on a long time ago was to always go with a size bigger. But don't go too big if you don't need it.
Good luck and hope this helped also.