Yes this happens, especially at the DI level. DI sports is competitive, and plenty of head coaches are let go or pushed out for performance, and their assistants along with them. But track and other non revenue sports are different than football/basketball.
1) Compensation is radically different for football and basketball coaches (and that is an understatement); thus expectations are different. That is how it should be. Where I work mid tier football assistants and all the basketball assistants out earn all the other head coaches (who all make relatively similar money). Even when these guys loose their jobs they still took home $250k over a three year period.
2) Different schools are able to offer different levels of support, but at least in football/basketball everyone is on equal footing in terms of scholarships. Not the case in track. Virtually all P5s are, but in the other conferences levels of scholarships vary. If an admin is not willing to spend scholarships they don't typically hold their coaches to a standard of winning. Look at conference results for non P5s and you can make an educated guess based on rosters and results on which teams have the full compliment of scholarships.
3) Administrators evaluate coaches different than you do. They really don't care how much the local talent on the team improves; they care about results, mostly conference meets. Development is immaterial compared to results.
4) It is expensive to fire coaches. You typically have to up the base salary for the head and maybe assistants and then cover moving expenses for multiple people. ADs tend to be far more practical when it comes to non revenue sports, and won't be trigger happy to release a staff only to have to sink even more money into a new staff that may not even be better (how often do teams in any sport radically improve after a change?)