If used wisely, it can be used to promote your blog in multiple ways.
If you have the SP to get your post enough value to get to trending it can definitely be used to promote your own blog. This can require having a lot of SP as getting on trending takes quite a bit of post value.
Having a lot of SP also can be used to vote on others blogs and in turn have them come check out your blog. Not everyone checks the big voters, but some users do and that can help your content get seen.
The SP can also be used to help communities and can be used to sponsor prizes for contests for particular communities. I've donated 200 SP to a community(as prizes to weekly contest winners) and I get a shoutout on their posts which in turn leads to a promotion of my blog.
So yes, having more SP can help your content get seen, but you can chose the way you want to use that SP to promote yourself.