Because many indications point to this being the case?
As many, many people already stated, the UI downgrade screams simplification for controllers. Need I remind you that time and resources were poured into the UI to make it simpler than what was already there. Aside from that, AI behaviour has stagnated compared to mods of the previous installments (PBoD, VC) despite this new engine. Furthermore, game design in general has taken a VERY simplified route. Of course, people can have opinions on these decisions, good or bad, and for the forums, consisting of many M&B veterans, the general consensus is written all over The Citadel.
This is not a fair comparison in the slightest! WB in and of itself wasn't very complex, but memorable. People were able to appreciate the passion put in its creation, with many of the rough, non-mainstream features working in its favour. Much of what made WB great is missing in BL, things that aren't necessarily difficult in concept (Feasts, manhunters, courting, INTERACTION, etc). Instead of building on to these, we instead were given a glorified battle simulator with click screens for management. Of course, people can have their opinions on whether they like this or not, console or PC.
Still, despite this, I agree that not every single feature that is taken out of the game is because of the thought for a console port. No, instead its just due to plain incompetence on TW's part, incapable of innovating and taking risks(ambushes, minor faction bases, sally outs, village upgrades, co-op, freelancer, etc).