This is not particularly true. Hypergolic fuel mixes are less efficient than LOX/LH2 (which is nontoxic (exhaust is water vapor) though still hazardous of course) and LOX/RP-1 (more or less nontoxic again. RP-1 is just fancy kerosene). The only real reasons to use them in first stages^ is that you can store them in the rocket (problematic with cryogenic fuels/oxidizers like LH2 and LOX since they will boil off over a short period of time) and the ignition system is simpler (not really a big deal).
LOX/RP-1 was actually used with earlier ICBMs like the Soviet R-7, the American Atlas. Storable hypergolic fuel mixes followed these, though now modern ICBMs are solid fuel rockets (storable, and safe for people on the ground).
Hypergolic fuel mixes have caused issues for non-military rockets too. During Apollo-Soyuz there was a leak of N2O2 into the Apollo capsule. Not a very good situation at all, but for that application they are really the best tool for the job. http://en.wikipedia.org/wiki/Apollo-Soyuz_Test_Project#Re-en...
^ Hypergolic fuels are also useful in engines that you need to start/stop multiple times, and in upper stages that need to store their fuel for a while.