Altcoin is very broad definition of any coin that is not a bitcoin. Thus, there are many coins that serve completely different purposes.

But even if you referred only to cryptocurrency altcoins, still they shouldn't be deleted. This is a free market, and that's the beauty of it. If a coin worth something it exists, if not - disappears with time.

Apart from that, different coins may have different jurisdictions, for example we see that some governments don't like privacy coins.