Not every writer is an editor, but all writers should know "how to write well" in order to actually write. However, that is why publishers and magazines and other places writers submit their work to... have editors. It's the job of the editor to help to shape your work to be the best that it can be. Readers don't want to read work that is filled with grammatical errors and doesn't flow well or have any point to the message.
Most people don't like to deal with criticism, whether it's physical, mental or spiritual. However, most people like to experience praise. How does this apply to your writing? If you're happy with your work and think that you're doing well, you may be less likely to seek out the assistance of an editor. However, if your writing is in a bad phase and you're not doing well, then you may be more susceptible to accept editing assistance.
Why can't we have it both ways-where we're open to criticism at any time, whether we're on a "writing high" or not? In my opinion, I think we can have it both ways. We simply need to be open to the possibility that we're not right all the time and that we can seriously benefit from the opinion of a meticulous and open-minded editor.
This aspect of dealing well with constructive criticism applies to how we treat our readers. For example, are we always telling them what to do in our "self-help" articles or are we educating in a way where we're treating our readers as adults rather than children. If your method of writing is more of scolding, that's not going to keep your readers as loyal fans.
Readers want to get reliable information from a trusted source and to be educated and entertained in the meantime. If you can't provide the facts, whether it's an article about How to use a netipot or even writing a chapter in your next novel, you'll soon lose valuable credibility with your readership. As a freelance writer and author, that is a situation that you do not want to find yourself in. Keep your tone light, yet informative and engaging and you'll garner a mutual respect between you and your readers. They'll continue to seek out articles and books written by you.
Not only do you want to write for your reader-base, but you also always want to write with your critics in mind. For example, if you don't provide the facts in your work, you have given your critics and easy opportunity to disparage your credibility-and if your facts are off, then these critics have every right to call you out. Wouldn't you rather have your work reviewed by a fact checker and editor in advance of publication so that you don't give your readers or critics any chance to call you out?