Lager with lime juice in it was "thing" in the UK back in the 60s and 70s. I don't know if this habit still exists.
Lager is not a beer though
Proper beers like ales or IPAs don't need lime for flavour.
I would love to see you have that debate with someone from Bavaria. If you order a bier you will get a lager by default, if you want something else you order it by name. Their lagers have more flavor than the typical American beer though.