The vast majority of the bloggers who Follow this blog do so because they are interested in developing and maintaining their Blogger blogs, and this blog - hopefully - provides them insight. Occasionally, someone interested in Blogger blogging- and Following a blog that's published by someone else who's Following my blog - will surf the Following community of that blog, happen upon this blog, and decide to Follow this blog. Generally, that will be because the new Follower is also interested in Blogger blogging.
In other words, I will gain a Follower who's interested in Blogger blogging, because this blog is also focused on Blogger blogging.
And, it's likely that other Followers will Follow this blog, because of their interest in Blogger blogging. So, it makes sense for me to advertise this blog in places where people interested in Blogger blogging congregate.
I have other blogs, focused on other subjects - cooking, miscellaneous jokes and pranks, and Windows Networking, to name a few - and various Followers to those blogs too. Most Followers to those blogs will have common interests - the Followers to my cooking blog will be interested in cooking. Relatively few who are interested in my cooking will be also interested in gardening, or in rap music.
To get Followers who bring more Followers, because of a common interest in the readership of our various blogs, I need to advertise my blog where it's content is relevant. Not where my need - simply getting more Followers - is relevant.
Were I to be desperate for Followers to my cooking blog, I might go into a forum about Blogger blogging, look for a discussion where everybody says
I'll Follow your blog, if you'll Follow mine.and add the URL of my blog to the list of hopeful bloggers. And I might gain a few Followers, from those bloggers. Unfortunately, those Followers, who publish blogs of varying interests, will have readers of varying interests. People Following a blog about rap music, and surfing the Following community for that blog, will be less likely to also Follow my blog about my cooking, because they aren't necessarily interested in my cooking.
I will, I suspect, be more likely to get Followers from folks who are interested in cooking, and who Follow other blogs about cooking and happen upon my blog.
And, once again, relevance brings readers.