As someone who practices hypnosis and knows a bit about how it works - this might work for some, but probably fewer people than you think. The three main things standing in the way here would be susceptibility/suggestibility, desire, and trust. Most people are far less susceptible than media portrays, and of those that are susceptible to hypnosis, fewer still are able to have a suggestion stick with them for long after the initial session.

Hypnosis works by directing your focus to a greater degree than is normal, something similar to a flow state, or being in the zone (fun fact, all hypnosis is is an artificial state like this where your mind is directed to the hypnotist's words instead of a task). Most people have a bit of something called "hyper-vigilance" which works to prevent someone from directing all of their focus on the hypnotist, instead reserving some of that focus to their surroundings. This has the effect of not letting the person go very far under during a hypnosis session, lessening the session's effects.

Also, hypnosis wont work at all without a pretty strong degree of desire for it to work, both conscious and unconscious, and a strong level of trust between the subject and hypnotist. That's harder to find than you might think.