That's just a lame excuse. It has no basis in reality.
Yeah it does.... If the ISP doesn't have SNMP/SSH/etc to the NIU device, then a truck has to be rolled to diagnose, even for an internal network issue.
Then the customer will not be happy when they have to pay the extra fee for the truck roll, plus the technician's time.
Also, for business internet: the cost is more than enough for the ISP to supply a basic CPE for free: However,
it's the ISP's property, and important that it is the ISP that has eyes on and manages this point where the ISP's network ends and the customer's begins.
There's absolutely no reason for an SLA-free Internet service to require you to rent a modem.
SLA-free internet service is not business-grade internet; I'm not sure what that is.
There Should be an SLA, if you are purchasing a business connection.
The problem is that Comcast uses a fundamentally broken and insecure technology for routing, wherein your cable modem has custom firmware with a crypto key in it that lets it do encrypted RIP for router advertisements upstream.
The technology used is a separate issue ( I think); that may be true in Comcast's case, but other ISPs have the same requirement.... RIP obviously doesn't scale; if they want to do that, then the protocol used should be IBGP.