Inner parts are very important. Just ask any conductor. A friend of mine who played lead on the Woody Herman Band told me of a guy in the band who just played section. And that he had a reputation of being one of the strongest section players in the business. So he got respect and work. In one of my bands in Germany, there was a woman who played 2nd and 3rd and didn't even want the chance to play 1st on easier parts. That was her thing and she played those parts for, I guess now, decades. And singing praises of the inner parts to a student who's playing them in terms of their necessity, is probably what one needs to do if that player is not going to progress. But given all of that, I still don't think the 2nd and 3rd parts are ones to which one should aspire.