Richard Strauss wrote about 200 Lieder, and only around 50 of them are part of the repertoire; the rest is hardly ever performed. We could say that’s pretty common, a composer’s complete corpus is rare in the repertoire, with the exception of composers such as Mahler and Duparc, who wrote just few songs. Those fifty Lieder are mostly performed with orchestral accompaniment instead of piano accompaniment; that's also normal, Strauss and Mahler fathered orchestral lieder. Some of these famous Lieder were not orchestrated by Strauss but by other composers during his lifetime. I understand that he was aware of that and consented. One last thing: among the Lieder that Strauss composed originally for voice and orchestra, only four are performed on regular basis.