Plus, with all due respect to the pole vaulters, it's probably a bit easier to break records in that arena.
Not in the men's event. Bubka, for reasons of natural ability, brilliant technique, or otherwise, was miles ahead of anyone since. 6.14m is massive, and a full 10cm higher than the best jump in the world last year.
The women's is different. The reason the record was broken so very many times over the last decade is that it was effectively a brand new sport (first in the Olympics in 2000, and only started at any level about 10 years earlier) so no talented athletes had previously devoted their careers to it.