In my experience, SSO is a requirement for some corporate clients. So depends on who you are selling to (individual employees or orgs who will have a number of their employees use the software). For example, if you sell a quoting tool to a department, which will then be used by their salespeople, SSO requirement is a possibility. If it's a small app that the CEO will use to schedule posts on Linkedin, then there is no need.
In my experience, login using Google, Apple is a convenience feature that may increase conversion rate if the product is sold to individuals, but is not essential.
Your experience may vary.