Back in 2019, OFGEM conducted a review into how various costs are recovered:
Ofgem publishes decision on Targeted Charging Review.
www.ofgem.gov.uk
In brief, this review moved a bunch of fixed costs from the unit rate over to the standing charge, making the price of energy more representative of the actual costs involved. The changes were supposed to come into effect as of April 2021, but got delayed a year through to April 2022.
There's a campaign by Martin Lewis & MSE to have the changes reverted to help lower income households reduce bills.