Krillin is a special case.
Again, Gohan went through intense training for a year and he honestly thought he would do nothing but watch? In that case, Goku wouldn't have bothered
Gohan saw himself as Goku's sparring partner more than anything else. Goku failed horribly at understanding his own son. Like Rutger said above, Goku assumed that Gohan was just like him and loved the challenge of a good fight, when this is obviously not the case. Goku should of communicated what he was trying to do, instead of making false assumptions. Gohan ain't a mind reader. Goku should have just told him the plan, and spent the whole year prepping his son to be the one to face Cell.