For a long time in the last two centuries (possibly starting with Kant, via Frege until today), philosophy tried to "lead" sciences and settle the paradigm for science's validity. Nonetheless, mathematicians and even more applied scientists kept on doing sciences irrespective of whether their fields of investigation were deemed to be "non logically justifiable". So, why did philosophers keep on asking themselves questions about the logical possibility of, e.g., mathematics? Why did epistemology develop at all? Because philosophers could not help doing so, since they were inquisitive human beings, keen to understand and not just to act in their world.
I would like to argue that Mīmāṃsā thinkers fulfilled a similar role in Classical India. They inquired about sacrifice, although the actual performers of sacrifices (as proven, among others, by Daya Krishna) did not take their texts into account. They inquired about sacrifice although their thoughts had no practical impact, just because they were intrigued by the issue.