It's not about the profits, but about consoles being a trojan horse/loss leader to widen the scope/breadth of your ecosystem. AppleTV hasn't been a resounding success, which is why such acquisition could potentially make sense (not that it necessarily does). Microsoft/Sony have what Google/Apple do not; an access to your living room.
Microsoft could scale back their console efforts if the X1 fails, but unless the failure is catastrophic (i.e. Wii-U type), X1 / 360 still represents a big part of their consumer ecosystem strategy - selling it would definitely put an end to these efforts.
The tablets and smart phones in people's hands while they watch TV constitute better access to the living room than any game console could hope to offer.