Why is msl code needed on an unlocked phone

[AC Question]

I purchaed an unlocked Samsung Galaxy s8+ from Samsung directly. Once I put in the Sprint SIM card, when I try to get to the ##data # menu and want to edit it, it ask for an msl code. Does anyone know why?

 

[Ca_lvn]

Not sure but MSL is usly to be able to change advanced settings like apn
I used to trick sprint chat into giving me my MSL number then in advance setting I could turn on Hotspot