It's possible you're not properly distinguishing between alt-coins and what could be classified better as bitcoin blockchain forks. Maybe the design differences are mostly not very inspired, but some may have features that make them incompatible with the bitcoin keypair specification. The argument for alt-clones breaks down for a coin like that.

Don't get me wrong, I'm not a big fan of alts (have never held, nor mined, any alts). But if an alt came along that solved the bitcoin pseudonymity issue, and still had the flexibility and running costs of bitcoin or better, I'd seriously consider changing allegiance to that.