The Lufthansa situation with 25% earning on L/K/T fares is a fairly recent program devaluation (it was announced in fall 2013). UA may continue the status quo (earn more miles for LH T on UA than on LH Miles&More), or they may re-align in a year or two. In the race to the bottom, some carrier has to be the first one to cut benefits and see if everyone else will follow. In this case it was Miles&More who cut first.

I wondered exactly this same thing about Turkish Airlines and W/P fares a couple of years ago. "If this credits 100% to United or 25% to TK Miles&Smiles, why would I ever credit to TK?" Eventually UA fixed it for TK — there were issues crediting the miles and eventually it was changed to a flat 0%.