If the workforce is remunerated better for their time, I think it will have an eventual effect on MSing. Payments and reimbursements being what they are today is largely a result of the financial crises dating back to '07-'08.
When I first started MSing, wages were higher than now and purchase/returns were rare, rather than the norm. Many shops had generous reimbursements because they were trying to entice the existing workforce to to shop in their free time. It wasn't something that was easy to make a living at, but the quality of work as a 'lifestyle shopper' was much better.
When a large amount of unemployed workers suddenly were available for shops and had the attitude of 'something is better than nothing', pricing and reimbursement structures changed. That change was slow and and I think and return to the previous model will also be slow to be adapted, but when MSCs can no longer find shoppers to take $5 shops, it will have to change.
BTW, when I was employed a shopper in CA a few years back (by a company that no longer has an employee shopper model), I was paid more than $15/hour. I think the payment structure for a shopper that attempts to shop full time should be based on earning an average of $15-25 per hour for their time (In California, at least).