the arrangement sometimes suits FI's as it allows them to Foxtrot Oscar at short notice if something better pops up.
The thing is that an employee can FO at zero notice anyway and there is nothing whatsoever the employer can do about it. The employer still has to pay the employee for hours actually worked. Obviously the employee won't get a reference from that employer but he won't need one because he has already found himself a new job
The stuff about having to give notice works in only one direction: against the employer.
In the end, if the business is there, then various formulae will suit different people. If the business is not there, no amount of employee protection will do anything because the employer's business will go TU.