There are a LOT of jobs that are 24/7/365 ... solider, President, policeman, pastor, etc. These are callings, not jobs. However, to my mind, that alone does not justify requiring celibacy.
SnakeDoc
The exceptions just seem to be practical from what I can tell.
I have always been a little puzzled by the celibacy requirement (and this comes from a non-catholic). At least some of the apostles were married. I can’t imagine any current priest doing more important work than any of the apostles. It would seem to me that if celibacy was really that important that Jesus would have chosen 12 unmarried apostles to the set the example. Instead, the example we have is a mixed bag: some unmarried apostles and some married apostles.
The lesson I would take from that example is that either is acceptable.
You do realize that celibacy is a prohibition against marriage and is not to be confused with abstinence don't you? Can you explain why the military academies prohibit cadets and midshipmen from marrying?