There are various reasons why IRCC may request fingerprints. The primary and most common reason is probably to verify the applicant's identity, although this in turn may arise relative to various concerns.
For example, as already noted, there are often very similar names associated with the same date of birth, and IRCC may see a need to distinguish the applicant from another individual with a similar name in their database, or RCMP may need to distinguish a hit on a similar name in their databases (RCMP background check goes beyond name-based criminal records).
So sure, any criminal history is likely to trigger a fingerprint request, but any applicant who does not have a criminal record has nothing to worry about if IRCC requests fingerprints. Many participants in this and other forums have reported minimal delays in processing their application after responding to a fingerprint request.