Pit lane is crowded enough as it is
Well there is that
They are.
But the stewards prefer to sit around for the whole race and then hand out grid penalties.
Things like jump starts and speeding in the pit lane still carry an automatic drive through.
See, I'd like to see offenses handled in real time, ie drive throughs, stop-start penalties etc - the problem with handing out grid penalties for the following race means that the teams can "manage" it to a certain respect, for example last year when Massa's gearbox suddenly needed changing, allowing Alonso to start on the cleaner side of the circuit. If a driver is penalised as soon as possible, it has a greater impact on their race, and perhaps their season. It avoids the seemingly random penalties after a race and maybe some of the controversy over the steward's decisions, i.e. penalising a driver with a 3 place grid drop, as opposed to 5 for an equal offence earlier/later in the season.
I think that modifying the cars from Race Control (limiting boost for x number of laps etc) makes the FIA very open to criticism when it comes to selectivity (Not forgetting what "FIA" has been jokingly referred to as being the acronym for...) - it also opens the window for other "modifications" to be made to the cars, for example mid-season they may being in a ban on DRS or KERS etc (spit-balling here..).
It seems an overly complicated penalty system for what is a simple problem; if you break the rules or cause danger to other drivers, you are punished accordingly, and during that race (extenuating circumstances notwithstanding) - this leaves all the heresay and scandal out of it, once the race is finished, the matter is closed, move on.