The subs for those alternative providers have similar tiering but more generous token allocations than Anthropic and OpenAI, and deliver good enough quality to be worth it.
If I needed to fall back on OpenRouter, it'd be paid per token, of course, but that'd take 4 major providers being down, in which case I suspect I'll have more critical things to worry about.
As it is, I use more than I could with a single $200 Claude Max subscription anyway, so I distribute my tasks across multiple providers.
Even without that it's cheap insurance given the cost of lost time.