This is really a Good Question to be asked in Blackhat SEO forum
Why because, There are two popular ways or methods to do SEO.
1. ‘White hat’ method
2. ‘Black hat’ method.
You are either of the two or you’re in between.
Black hat SEO are against the search engine's terms of service - Though there may be some short-term success through increased traffic to your site, Google penalties are getting more and more sophisticated and can have devastating effects on your rankings and traffic.
Because it helps to rank faster. You won't find any niche where some people are not doing Blackhat SEO. Whether it is buying legit guestposts or if its blasting spam links on a website. Taking action to improve the rankings manually is always "manipulating" the algorithm. Also it is very hard to define "Blackhat". Everyone got a different opinion about it. Of course, if you have a budget of a few millions and lots of connections I will just pay CNN, BBC, Forbes etc. to make backlinks and advertising for me. If I don't have this budget and connections I will just look for decent PBN domains and create my own high authority sites to link on my site in order to improve my rankings.