I do not like large lumps of meat, so rarely cook large joints, never eat steaks and rarely eat burgers and the like, so have very little need for a meat thermometer. When I do cook meat, I like it very well cooked, no pink meat for me. The Christmas turkey is cooked until it is difficult to put on the carving dish because it is falling apart, and I have no problem with the flesh being dry.
For food in the microwave I use the testing whether a cake is cooked method. Stick a small sharp knife in and feel it when it comes out. If the temperature isn't even the length of the knife, it needs more cooking. Again I rarely put large lumps of food in the microwave. I will be putting a large plastic box of partially thawed stewed apple in the micro wave today, but that doesn't need a thermometer.
I can see that such thermometers may be very useful for those who regularly cook joints or other large lumps of meat.