Prohibitive parking is certainly an issue.
Where I live, in Stoke, there was a massive municiple car park that charged a ludicroulsy high daily charge, penalising all office and shop workers who avoid the unreliable and unpleasant bus service to get to work.
Then Tesco appeared - built on of their European superstores, and took over the car park, limiting free parking to two hours to suit their shoppers, giving the council no revenue whatever.
There is litle wonder that town centres are dying - shopping habits are altering, but a simple inability to access privately owned shops will simply strangle them - quickly.