If social media platforms show your posts to more people, that’s more eyes on what you do and more potential buyers.
If they show more of your content to the same people, those people are reminded of you and what you sell on a regular basis. The more that people are exposed to your brand, the more likely they are to buy from you when they need what you sell.
Also, if these people are engaging with your content, it’s a signal that they like it, or find it interesting enough to engage with. If people feel like they are getting something valuable from social media interactions with you, it can contribute positively toward how people feel about your brand overall.