No criticism of the MKE2 (I haven't heard the MKE1 yet but have heard good things about it) and it's certainly considered a workhorse in the theatre sound industry (edited to add "along with Countryman"). However, the DPA is considered a little better for some applications and many's the time I've heard sound designers say "I'd like to have used a DPA but couldn't get the budget". Certainly, in the configurations and quantities used for big shows, the Sennheisers are about 30% cheaper.
Just as an aside, in the theatre world, the "tie mic" is rarely used on a tie. It's more likely to be up on the hairline or over an ear. Omnis are almost always used in preference to directional versions. On the other hand, in TV, where lavs ARE used on ties or lapels, for some reason Sony have a huge market penetration. The ECM77 or ECM88 have a huge segment of that market. I've used ECM77s in the hairline/over ear position and they worked well but have never managed to break the MKE2's popularity in the theatre--I guess it's a bit like the SM58 of the musical world..."I know I can get better but everyone knows how to EQ an MKE2" sort of thing.
However, just to offend your sensibilities, between sweat and enthusiastic dancing, the service live of lav mics in the theatre is very short. In the past few years, there's been a move to use very cheap Chinese mics. They're far from as good as the Sennheiser/DPA/Sony type but can sound okay with some EQ--and at under $30 a mic, they become a disposable like batteries instead of a capital item. Producers love them for that!