The performance of this can matter in some scenarios. In embedded systems, smart cards etc., generating the primes can take a significant amount of time (15-20 seconds typical) even with the 'low' number of iterations. Higher iterations means the user will have to wait even longer. Actually, in such systems it is not unusual to see occasional time-out errors and such when the smart card is unlucky with finding the primes. The timeout value may be a fixed, general value in a part of the stack difficult to change for the specific call.

Another case is short-term keys/certificates, where a fresh key pair is generated, and cert issues, for each and every signature. This setup makes revocation easier to handle (the certificate typically has a lifetime of a few minutes so it is 'revoked' almost immediately).

There are also scenarios where the keys are generated on a central system (HSM's etc.) to be injected into a production line or similar. There performance can matter as well. I worked on a system where the HSM's were used for this. They could typically generate an RSA key in 1-2 seconds, so 12 HSM's were needed to keep up with demand - and this was again with the reduced number of rounds.