Because lambdas offload programmer work to compilers.

Think of a piece of code like:

  array = [1..10]
  evenNumbers = array.where(x => !(x % 2))

Now think of how to write that code not using lambdas.

In Java where people seem to like typing unnecessary stuff it would make sense to not have lambdas as then you can type extra stuff. Also lambdas would reduce KLOCs thus making teams using java with lambdas less productive.

This is similar to the reduced productivity seen by teams using scala or clojure on the JVM.

Also, OOP has nothing to do with procedural or functional languages, it's completely orthogonal.