I couldn’t really give a shit as I don’t really like shopping and don’t work in a shop. BUT….
People do like shopping and people do work in shops and some people like having varied part time shift patterns that can be accommodated on weekends. Young people who have school or college during the week but want to earn more money would be happy to work additional shifts at weekends etc…
Making Sundays just the same as the rest of the week opens up possibilities for changes in shifts, It doesn’t mean that if you already work 3, 4 or 5 days in Tesco, you’ll be forced to work 8 hours on a Sunday as theres plenty of other people that need jobs that would happily take up that slack.