Have an umlaut on my surname but have never managed to get it on any official documents. Bank statements, chequebooks, medical records, payslips, pensions - nobody seems to be able to do it so technically my name is/was incorrect on all these. Should I complain to the European Court of Human Rights (she asks tongue in cheek)?
I wouldn't say letters with umlauts are in decline here so much as the fact that there is a growing acceptance that internet addresses etc. can't cope with them, hence it is perfectly normal to use ue for ü, oe for ö or ae for ä as far as computers are concerned. I have an ü and an ö in my address and I don't think that is going to change, but website addresses can't cope with umlauts so that is when they are normally substituted.
Doch! öüä. But I bet yours doesn't, and if you want to access a German website you'll find it a lot easier to use oeueae, as will most of the world doing business with Germany.