Altcoins: because maybe a global transaction register doesn't scale so well after all.
Because you invested hard cash into an ASIC and now have no options ?
except for one.
And there is an evolution under way, which will likely soon make it obsolete? (along with your investment)
:: (
ASIC have many options.
You can choose to merged-mine the full panoply of all the SHA256-merged-mine-able coins, or you can choose any combination of them to merge, or if you want to earn less than you could you could choose any one of them, such as bitcoin, and mine only that one.
-MarkM-