People on salary earn a fixed amount per month - they don't get paid extra if they work an hour longer in the evening instead of shopping.
People on most hourly jobs have their schedule set by their manager. They can't pick up an extra hour of work unless their manager has some to offer, and not at the time of their own choosing.
People working on their own businesses have an even less direct correlation between extra hour worked and extra income.
Only the very few people who do remote freelance work on an hourly basis have the flexibility to decide between going shopping for an hour or doing billable work for an hour.
For everyone else, the opportunity cost of leisure time is close to 0, but they might be willing to pay for services for other reasons.