I think long ago I've read somewhere (possibly the Colin Irwin book) that besides the contractual obligation for another album MK felt like he owed it to the other DS members (and I think in particular John whose father financed their break-through demo) to give them one big final opportunity to capitalize on Dire Straits with a last studio album, big tour and live album. After that he could abandon DS with a clear consious and just only do what he wanted, how he wanted without feeling any moral duties towards the DS team. I suppose in that respect the formalazation of Dire Straits being MK, JI, AC & GF (and EB's position in Dire Straits Overseas Ltd) should also be seen seen.
Of course I don't if this is true, however to me seems plausible and even quite likely for it to at least have played a role in MK's considerations (amongst other things) .