Many friends of mine, readers, and also you might be asking why my blog is still on a blogspot subdomain, for sure having a top level domain (eg. .com, .net, .org) for your blog will make it more presentable, easier to memorize, will look more personalized and as others says will improve the SEO of your blog. And you might also be curious why my blog and other more successful blogs do not want to park into a TLD despite the benefits I’ve told above.
And the sole reason is that, it is in contrary bad for your SEO, although parking to a TLD has negative effects only for those blogs which ran for long time already, or what we can call "already established blogs"; with decent number of traffic. But for a new blog with no or little traffic yet, you can safely park it immediately to a TLD. I found out from many other bloggers that parked to a TLD had greatly dropped off the traffic of their blog, and they advice making a new blog with your domain instead, but for many who do not want to abandon their present blog, we stick with a subdomain instead.
I for one do not want to park a TLD for this blog, and instead planning to create a better blog in the future.
So if you have a blog under a subdomain and already have a good SEO, going to a top level domain is not necessary anymore. I’m pretty sure like me that’s just one of your first blogs and you can always come up of a better niche or a new blog.
But if your blog is till new, it is always better to get yourself a top level domain as early as possible, or else you'll also regret it later.