Java

Scala does have a way of specifying co-/contravariance, but Java actually does have that, too. In Java, you write <? extends T> for covariance and <? super T> for contravariance. Well, and generally, Scala's generics are compatible with Java's. It's quite common to use Java libraries in Scala.

One example where type erasure causes problems (which should be the same in Java):
Imagine, you're managing sensors and all of those sensors have a generic to remember what element will be produced by them: Sensor, Sensor etc.
If you want to keep all of those Sensors in one big list/map, you end up with a Sensor when you take them back out.

To retain type information, you have to put them into individual lists or somehow place a runtime type next to each element in the list, from which you can determine what to cast to.

I guess, in languages without type erasure, it doesn't let you place a Sensor into the same list as a Sensor to begin with, as those are strictly different types.
But of course, those languages may offer ways of doing type erasure anyways, and obviously, you can fall back to a common interface/supertype, if the types have that.