It’s different when targeting a specific business as that kind of boycott can continue indefinitely. A boycott against spending any money or going to any business can only last so long and therefore companies will see a downturn and then probably a spike in sales as people buy a bunch of stuff at once that they were planning to buy during the boycott. I agree with the other comments that organizing workplaces to eventually form the base for a real general strike would be a more effective strategy to actually hurt businesses.