Suppose a user operates their own separate website, say, a photography website. And suppose they include links to it in their stackexchange.com profile. Is there then Search Engine Optimization motivation to post questions here? Why am I asking? I'm baffled by the utter lack of detail in many questions.
Links in people's profiles always have a "nofollow" attribute applied.
The only link that has the "nofollow" removed is that specified in your "Website" field and then only after you earn 2,000 reputation.
The reason links are marked "nofollow" in posts is to avoid Google thinking that Stack Exchange is a link farm.
So, to answer your specific question - there is no SEO motive for posting links in your profile.