I was wondering about something completely different, when it occured to me: electronics and programming are probably the only sciences that you can do at home at a professional level and have a aren't purely theoretical (practical as in: you can see the results and they aren't purely theoretical, like math).
It's really simple: You CAN do physics at home only to a certain level - you can do the few basic experiments (say, pendelum measurements), and, well, that's all been already done a century or two ago. The more advanced physics require a lot of very expensive equipment, which is powerhungry, and can be very dangerous (radioactive, gigantic - can crush you, high voltage...) and you'd most likely have no place to put it anyway. Also, a lot of the equipment is very single purpose (not counting ofcourse stuff such as lasers, weights and stuff, but big macines, like, say, particle accelerators). All of this makes more advanced physics (IMHO anything beyond the stuff you did at high school) undoable for the amatuer. Ofcourse, there are also exceptions, say a guy that made a fusion chamber in his basement, but that's more of the exception that proves the rule.
Electronics are ofcourse only applied physics (well, part of it anyway), but still... they are two separate things.
In chemistry - well, the "Home chemist" labs can't be very extensive as kids might get torn apart from fun. Or high power explosives. All you can do at home (reasonably safely) is basic inorganic and a bit of organic chemistry. Advanced chemistry is really undoable due to a lot of special equipment required, as well as safety some safety issues - explosions are fun, but your mom might not agree. The same goes for poisons, acids etc... The unavailability (or very limited availability) of various chemicals is also a problem - if cyanide is needed, try getting it, and safely transporting it home without being suspected of a wide variety of criminal offences.
A problem with these might also be that you'll most likely not do anything really new in home conditions. From physics you'd be able to recreate various experiments, but nothing new. As for chemistry - good luck! Both of these areas would be far better suited for study on academic grounds - on a university or such. But simply not at home for practical reasons.
That's why electronics and programming are so popular - you can do the really advanced things with a quite simple and cheaply available set of equipment - a PC is a must these days anyway, all the software is freely available on the internet (PCB design, compilers, operating systems, simulations, dev tools for a wide variety of MCUs) and everything is well documented and supported. As for parts for electronics - there's a bazilion different shops for, well, basically any part. The same goes for tools for electronics - a screwdriver, a soldering gun, some solder, a multimeter, and, say, 5 other things are relatively cheap - and as you'd progress, you can make your own, or buy better ones!
Sure, in electronics you'll need to be in a big organization to get to the utmost top of the field (as in radars, space equipment, PC motherboards etc.), but you'll get to a far higher level alone than that which you would be able to achieve alone in, say, physics or biology. The great complexity of home made projects astounds me - computers (made from relays, or 74xx logic), CNC machines, lasers...
The same goes for programming (although Open Source is breaking this barrier as well) - to get to work on a project of gigantic scale, say, Windows you need to work at a massive company. Although anyone can contribute to open source projects. So programming is possibly even less limited - or, more precisely - you are less limited to the projects of your choice.