MurmurHash isn't secure and isn't intended to be. The algorithm is intended for fast non-cryptographic hashing for non-secure hashing needs. Whether or not people will use them only in cases where they really don't need any security in their hash (an attacker could cause a denial of service or a slowdown of service by degrading the performance of core data-structures if you use a non-secure hash function against untrusted inputs in the wrong contexts) is somewhat up in the air.

That said, it's being used by real applications in production, so the niche is definitely there, but for anything that needs any level of security you should continue using a secure hash algorithm, of which the unimaginably named SHA family provides a good set of standard algorithms. Using a secure hash every place you need a hashing algorithm unless you know you'll need the extra perf and know you can get away with it is probably a reasonable practice.