Let's Build an Encyclopedia
The goal of Stack Exchange is to form an encyclopedia of knowledge that's helpful to future visitors for years to come, using a Questions and Answers format, and every time you post a question or an answer, you're planting a seed that helps grow that knowledge. It's important to recognize that most of the people who visit Workplace SE aren't people with actual accounts. Instead, they're people with real problems who typed that problem into the Google search box and landed on one of our posts.
We never see these people nor do we directly interact with them, but they're there, watching everything we do and soaking up the knowledge we've built here. Many who create accounts know the rules just from watching us interact in comments, and the new users who know the rules are more likely to become avid users with 200+ reputation.
We're showing new users we're a Q&A site, not a forum
Some people may think of this as a forum because many questions feel like they could be a discussion. But forums are nasty places. Before Stack Exchange, I remember digging through noisy threads, oftentimes not finding my answer until page 18, 1/2 way down the page, after filtering out all of the "I have the same problem too" messages and other noise. Forums are actually just random snapshots of the Internet at a specific point in time. All those grammar errors, spelling issues, and clarity problems are forever stuck, forcing all future readers to go through the same steps that others went through in trying to find answers.
But it's important we fight the urge to delve into the discussion because it gives those future visitors the wrong idea. Eventually, some of those future visitors will decide that Workplace SE has helped them so much that they want to give back, and we want them to hit the ground running. If there's too many conversational elements in answers, users may not realize we're not a forum.
The easiest new user to deal with is one who already has an understanding of how the site works. Users who don't have that understanding, even when dealt with gently, may throw their hands up in frustration and leave. In fact, if you read posts from 1 rep new users, there's just something that feels different about those posts. They're sloppier, don't have good whitespace, and just contain a lot of aspects that one might expect to see on a forum, not an encyclopedia of knowledge.
Why do we remove noise
The information above about new user adoption is just one reason to avoid being too conversational in posts, but the other reason is to filter out noise. All of those greetings, salutations, thank you's, and other taglines tend to take up space and create clutter, not in the database :D), but on the actual page. They take up valuable screen real estate. Most of the people visiting this site see ads; they don't have the same experience as avid users, where Stack Exchange filters those out for users who create content. Just view the site in incognito mode to see what random visitors see.
Oftentimes, these taglines, greetings, or thank you's are put on their own lines. Which means we've introduced more whitespace and pushed more content down the page, making users have to scroll in order to see the big picture.
In questions, greetings are the worst, because they take up room on the front page, pushing out all of the important stuff. Imagine what the front page would look like if every post title was "Plz help!" or "Help m1" or "HEEEELLLPPP!" followed by more noise that tells us nothing about the actual problem. In short, this is also about making it easy for our community to moderate posts by maximizing our ability to properly vet questions and answers.
So should we edit this stuff out
I tend to take the approach of only intervening if there's a problem. If you look at my answers, I've probably included "Hope this helps" or something similar, but I try to make it a point of not putting that on it's own line so I don't take up unnecessary vertical space on the screen. If someone edits it out, so be it. I'd rather err on the side of less noise than more noise. But to maximize the use of space, you could just include it on the same line and know that if it gets edited out, just let it go. Less noise is always better than more noise. Hope this helps!