There's also another reason: these recount campaigns are making him a lot of money:
Where Trump’s recount fundraising dollars are really going
He's using his call for a recount as a fundraising ploy, but the vast majority of the money he's collecting is going to pay off his own campaign debt and to general revenue for the RNC; very little is actually going to a fund for recounts and legal challenges.
As soon as concedes, this flow of money stops.
If it weren't for him shuffling appointees around in Washington, I would probably assume that this is all about the money for him. Maybe it is.