Fuse (Main Electrical) / Circuit Breaker (Sub-Panel)

[Joshua Holt]

The commercial condo I'm buying apparently has a fuse electrical main system in the common space electrical room in the building (see photos). However, there is a circuit breaker sub-panel system in the actual unit. 

Any reason why I need to get the main fuse electrical system upgraded to a circuit breaker system? I find it odd that they aren't the same but (1) future commercial tenants won't have access to the fuse panel, which should prevent them from messing with it and (2) the circuit breakers in the sub-panel should flip if there's too much load, which means in theory the fuse in the main panel shouldn't ever to get the point where it is overloaded.

Are there other reasons why it makes sense to upgrade the main fuse electrical system to a circuit breaker? And if so, does anyone want to give me a ballpark guess at how much that would cost?