basically, when an audience claps for the conductor, he waves to the orchestra in thanks to them, for working with them and for them working with him. if they are truly 'one' then there is no difference between the applause for him and them.
sometimes you can see this connection take on almost superhuman elements (where they are so in tune with each others tempos, expectations, and melding with the solo instrument) that the applause is generally for all concerned. imagine these type of recitals are actually few and far between being that there is often not enough practice time for the orchestra, conductor, and pianist to work through difficult places. time and money constraints.
where is baron van swieten when we need him? the money of haydn, mozart, and beethoven - getting their works performed and with all the resources necessary (whether it was 120 voice choir - or large concert hall) was largely due to his donations.