True, some folks do go to Holland for other reasons.Probably not many off this forum (I'd still go but not as much) but a lot of Amsterdams visitors go for everything but cannabis, my parents have been a few times and didn't even know about coffeeshops until I told them
I am not saying that no one would ever visit Holland, if there were no coffeeshops, but we do know that the coffeeshops bring in most of the tourists. (A torpedo only has to punch a small hole in ship to sink it even if the ship is mainly, intact. Getting rid of coffeeshops would punch huge holes in the ship! Intentionally turning a huge profitalbe indusrty into a small one, does not make sense to me.)
Furthermore, the closing of coffesshops would indicate a sharp move to the right, and so the entire vibe of the country would be different. Hence, other non-cannbis-consuming folks, who currently enjoy Holland, might no longer be willing to spend time in a such an environment.
My family history includes the Netherlands and I greatly enjoy Holland, so I appreciate the Netherlands, from many angles. However, when looking at it from a strictly tourism point of view, I fail to see how they would bring in large numbers of repeat customers.
What are the main reasons for going on vacation?
To relax?
To sightsee?
To try something differernt than at home?
To educate oneself about cultural differences?
If these are some of the main reasons, then IMO, unfortunately, a Netherlands without coffeeshops, would likely struggle for tourists, given all the other competition.
Consider the cultural institutions (galleries, museums, historical buildings, natural wonders, monuments, and so on); There are some very nice ones in Holland, but so too are there in the UK, France, Italy, Germany, South America, US, Africa, Asia, Middle East, and so on.
Tourism Score: Other places 1, Holland zero
Now consider sun, surf, and sand. The Netherlands has some nice beaches. However, they can only really be used in the summer months. Places with much better beaches: Thailand, Mexico, Australia, Brazil, South Pacific, Jamaica (also has great herb) and other Caribbean countries, California, Florida, Hawaii, and so on.
Tourism Score: Other places 2, Holland zero
Consider winter activities: I can just imagine the advert "Ski the Dutch Alps".... France, Canada, Italy Switzerland, US, and so on all have great winter activity vacation spots.
Tourism Score: Other places 3, Holland zero
Thus, IMO, it would take an advertising genius to keep the Dutch tourism as strong as it is currently, with the coffeeshops.
As has been mentioned the "Dutch only" coffeeshops idea has been previously put forward and and shot down. It would bring up a huge mess about discrimination and human rights.
Finally, as we all know, prohibition does not work and, indeed, has severe negative consequences. To destroy an industry, with a policy that has failed everywhere it has ever been used, seems incredibly idiotic.