I have been know to set a receiver on 14300 for background noise. The MMSN is often mostly check-ins and marine weather reports, but that means operators are on frequency and hopefully listening for emergency traffic if/when needed.
It is kind of annoying when a contester or occasional QRMer parks like 1.5KHz away or even right on 14300. The MMSN has no priority over other comms other than actively holding the frequency when there is no actual emergency traffic, but I still tend to think of it as an emergency resource instead of the often typical more casual amateur net.