It's less of a gamble to rely on everyone elses fabs - then if one of them isn't doing well you switch. You minimise your risk further by having something fab'd at all of them (TSMC, Samsung, Intel) as then you have a working relationship with each fab and engineers who know how to use that companies fabs. If instead you have your own fab you then basically have to develop everything at that fab to make it worth it and if your fab sucks for a certain node your whole business suffers (see Intel).

Dribble:

It's less of a gamble to rely on everyone elses fabs - then if one of them isn't doing well you switch. You minimise your risk further by having something fab'd at all of them (TSMC, Samsung, Intel) as then you have a working relationship with each fab and engineers who know how to use that companies fabs. If instead you have your own fab you then basically have to develop everything at that fab to make it worth it and if your fab sucks for a certain node your whole business suffers (see Intel).

Yes, AMD was proof of this when they used to own Global Foundries. Their nodes were never competitive against Intel or TSMC and as a result power consumption was high and performance was lower than competing products. Since moving to TSMC, they are on to a winner.