The club can pay him weekly as opposed to signing a top CB for about 50-60m and then pay them more than 100k a week. Doesn't matter that Ole won't play him, the Glazers will be happy they don't have to spend extra money to replace him. I won't be at all surprised if we price Lingard out of a move and claim him as a new signing also.
The money men is a big reason why we keep making these kinds of contract extensions. Either we sell players for big money, or we keep them around so we don't have to spend millions in transfer fees and signing on fees to replace them.
In the LVG days, many around here were heralding our new found ability to sell players for more than what we did in the Fergie days, because of the impression that we weren't going to be fleeced anymore. I always felt that was the wrong way to look at things.
United is a big football club and needs to be successful on the field. We were never a selling club under Fergie. Most players he sold were sold for little money because we sold them for footballing reasons, not for us to turn a profit or balance the checkbooks. Fergie also sold players who'd been great servants of the club for a pittance to not hinder their playing careers. In simpler terms, Man United used to sell players not for financial reasons.
Nowadays we keep on players we don't necessarily want just so we don't have to spend money replacing them.