I used to work for an electricity company before the market opened and then after it did. You don't own the meter, it belongs to the local energy company and they can and will change it to a prepayment meter in a heartbeat. Even if it is inside your property and you refuse entry, they get a warrant, break in, change your locks and charge you for the privilege.
Yes the monthly direct debit is the preferred method of the company because previously bills were produced quarterly. You get the discount because they get the money every month, you benefit from having a set amount to pay rather than lower bills in summer and higher bills in winter. Now you can have your bills monthly, mine are.
The biggest push for setting customers up on DD was quarter 1 so Jan/Feb/Mar following most people feeling pretty skint after Christmas. Your bill is so many hundred but hey you don't have to pay it all now, set up a DD at X amount and spread that bill across the year.
Also we used to write to the neighbours of anyone who had left owing money. Someone always pissed off a neighbour and so tracing that debtor made it easier if we had some idea or an actual address of where they had gone. I distinctly remember one customer ringing gleefully to guess that their neighbour had left owing money. I wasn't able to confirm that but he was saying good, you robbing bastards, I hope he owed thousands to you. I asked him who do you think pays for that customer? Do you think the company says, it's okay, we'll just swallow that debt? Or do you think that we cover losses like that by charging everyone else a little bit more for their bills? Like shops do to cover theft. He immediately gave me his address.
I will continue to pay by DD because that works for me. If companies go bust there is just less competition and less fighting for customers.