Here is why:
Social media platforms such as Instagram and YouTube were not built for instant sales (not even for eCommerce, although the platforms are fixing that now). They were built from the bottom up for community building, where the community building is focused around ideas, attitudes, specific emotions (love, hate, blushing, …) about a specific area.
If you want to succeed on social media, work hard to bring a dialog about what you do/preach. A hard sell approach is not suitable… Instead, bring the people together, and maybe down the line find ways to convince them sign up for your “mailing list.” Now – mind you – “mailing list” in terms of social media doesn’t necessarily mean an email list. Rather, make them become engaged followers and community members.