Above all, because it is fun. If it isn't fun, and I'm not getting paid, in general I am not doing it. Also because it is interesting, though that is really a sort of "fun". Any hobby can be turned into work -- and that is to be avoided. If you turn a hobby into work, it won't be long before you abandon it and go do something else.
Why micromounts rather than some other sort of mineral collecting?
There are many reasons. It avoids making mineral collecting a "money game" for one thing. Most mineral species are only found well crystallized in micro sized crystals. Very few locations yield good large specimens whereas micro material is fairly abundant. The smallest crystals are the best. At least really good micro crystals are much more common that superb big crystals, and for most species, it is micro crystals or go home.
If you want to collect big specimens and have plenty of money, don't let me stop you. But collecting micros is not about economy, that is just a sort of fringe benefit.
Most of the best mineralogists are micro collectors. If you look at photos on mindat, almost all of the good photos are of micro material. Most photos of big pieces look like clunkers, though in part the issue is that it isn't easy to take a good photo of a big specimen. It isn't easy to take a good micro photo either, but that is another topic.
Someone once said that if you go to most shows and exhibits and know about 100 minerals you will be able to recognize almost everything. To go beyond this, you have to get involved with a microscope. If you look at a typical "species collection" you will see a bunch of ugly clunkers with fancy labels. If I was going to be a species collector, I would do it as a micromounter.
Most micro collectors are nice people - generous, friendly, and helpful. There are few snobs and jerks, though I am sure you can beat the bushes and find some if you work at it.
Tom's Mineralogy Info / [email protected]