To me it doesn't sound so "economically convenient" to pay extra usage to alternative providers while someone pays 20/100/200 dollars for their service.
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.