I suspect it's because the standing charge is a way of increasing bills by stealth. A lot of people don't know how fuel bills work (not a criticism; it should be taught in schools because it can be tricky to work out/compare) and it's easy to slip in an increase to the standing charge in the hope that people won't notice too much or understand what it is.
I strongly suspect "network costs" and "balancing charges" translate as "Our profits are non-existent or not big enough so you're going to pay for it". See also: hikes in direct debits which are, in effect, a nice little nest egg for energy companies. These seem to be calculated along the lines of "We estimate your usage to be X and we'll ad on 30% so that credit you accrue sits on our asset sheet".
From a thread on the subject yesterday:
For those who have had suppliers increase their DDs, you don't have to accept their estimates or changes. My supplier tried to double my monthly payment and I logged in to edit it back to what it was because I prefer to have a small DD and then make a manual payment for anything over and above that. Of course, that only works if you want to pay that way - some would prefer to average things out over the year, in which case a DD that is, in effect, your yearly usage divided by 12 works fine.
My electricity account is only ever in a small credit (over the summer when my usage is less than my DD) or at zero balance (in winter, because I give a monthly reading, get a monthly bill and pay that sum less the value of my DD). I refuse to allow my money to sit in a supplier's bank account, not least because they can be sly buggers about giving big credits back. Of course, they always witter on that it's in your interest but really it's in theirs and they can fuck right off with that. On the odd occasion I've had a supplier quibble about reducing a DD I've offered them a choice: reduce the DD or I'll cancel it. They've never once chosen the cancel option.