There's loads of factors at play. Triathlon was mentioned earlier but that's mass start and the difference between 35 starting and 55 starting isn't that much logistically. The same way they're going to allow over 80 now in the marathon in Athletics. Others are a bit more difficult to keep a rein on but they've even tightened up in swimming with the removal of the B time automatically allowing A time holders competing in multiple events.
There are plenty of sports with only one entrant per NOC too; sailing, rowing, weightlifting and all the combat sports.
All of which is to say that we all have our favourite sports, and we all know which sports give our countries a better chance of medalling, but it's not an easy job for the IOC and the sports federations. It's OK that we don't all get our wishlist