Most fencers want to devote more time to national and international fencing to give themselves the best chance to make the Olympics, since only the Top 4 in the given discipline will make the Olympic squad.

For example, ND's Chase Emmer took the year off likely to devote his time to the Junior World Team and the Olympic team. Competing at both levels usually means 3 weekends a month that he needs to travel simply for national and international fencing. He would also have mandatory national team camps to attend. Adding NCAA fencing (and school) to it would make it too much of a grind.

The two Harvard women's foilists, Guo and Scruggs, decided to stay in school since they were high enough in the points standings (especially Guo as Canada's top foilist). On the other hand, Weintraub at Princeton and Rhodes at Columbia took the year off to mixed success. Weintraub will compete in the Olympic team event, but not individually since she finished the year in 4th place. Rhodes ended the year in 5th, so her only Olympic opportunity will likely be as a sparring partner in the lead up to the Olympics.

On the other hand, Bryce Louie at UPenn had intended to take the year off to try to make the US Olympic team, but after seeing the likelihood dwindle due to strong performances from the top 4 men's foilists early in the season, he decided to remain in college this year. It paid off well for him since he won the NCAA Championship today.

It is not a phenomenon limited to foil, but it is a discipline in which many of the top fencers are in college. In epee and saber, many of the top fencers (with a few exceptions) are either older than college age or still in high school.

(1) the amount of time you can commit to training and (2) the quality of competition that you can train against.