The marketing guys just love big numbers. The bigger the better. The higher speeds are useful for computer to computer connections through the access point or router. This is good for file transfers, backups, and gaming. If you have a local video server (i.e. TIVO), speed is even more important. Not all traffic goes via the internet.
Incidentally, the real thruput will be about half the connection speed.
One of the interesting side effects of the 108Mbit/sec routers is that it has forced the manufacturers to use high performance processors in the routers. That's normally not a benifit until you activate a large number of rules, services, and features which causes the processor to get overloaded. Basically, they run better in complex configurations.