Captcha is easlily bypassed by "captcha data entry workers".

https://moneyconnexion.com/captcha-work.htm

Nearly half of the world's population which is more than 3 billion people live on less than $2.50 a day.
(Source: https://www.dosomething.org/us/facts/11-facts-about-global-poverty)

Captcha won't deter spammers or scammers - but it will annoy plenty of genuine forum members.

Just a few words about captcha. Have you ever seen an entire Chinese (or another Asian, African whatever; it`s just for example) village solving captchas for bots? I have  $1 for 500 or smth it was. There are still services that provide such help. So I don`t think, this will completely solve the case. But indeed it can make a life more difficult for spammers. And for regular users as well