....and there we all were thinking it was the future.
I'm not sure what 'investing' you think is going on in Europe, but MLS has been operational at LHR, and only LHR, for years, and a significant proportion of based aircraft are equipped. The 'investing' took place years ago, so why wouldn't we use it to gain benefit from it while we can?
It has also allowed the validation of many aspects of procedures that will equally apply to GBAS, such as optimised operations in LVP in terms of a landing clearance trigger line and mixing ILS and non-ILS traffic in LVP.
While I agree RNP/GBAS/SBAS is the future, I don't think use of MLS at one airport in Europe has been a major delaying factor here.