Probably to minimize the possibility of having "sequence gaps", for example in cases of shutdown abort or flushing the shared pool.
Less probably to somewhat preserve space in shared pool (library cache) - that is perhaps more of a theoretical than a real life excuse.
In any case, you would use NO CACHE only on sequences that are fairly seldom in use, not on those that are under constant pressure.
ASCII a stupid question, get a stupid ANSI
24 hours in a day .... 24 beer in a case .... coincidence?