Well this could explain some things.
[Image via Arizona Department of Corrections.]
“Harry has told Kendall that he will not appear on ‘Keeping Up With the Kardashians’ under any circumstances. Harry does not want his love life played out across the world on TV. Naturally, the producers want Harry on camera.”
Keeping his private life private is obviously one reason, but it most definitely wouldn't be a good career move for Harry to flaunt his devotion in front of his millions of lovestruck lady fans!
Anyway, if we were Kendall, we totez prefer to have Harry's handsome mug behind closed doors. LOLz!