If that was the best solution then the pest control companies would do that, except they'd try to buy the spray in bulk straight from the supplier and use their own permanent spraying devices instead of buying a series of cheap disposable cans that force them to bend over all the time.

To some extent our notion of what's "professional" is dictated by past experience of professionals using what works best for professionals. If that changes, an unofficial pest control business has a pretty low barrier for entry considering there are literal DIY solutions at retail.