Without going over the whole thread, I'm sure people have mentioned : DMing is hard, it takes time, and it takes a lot of work.
Though I doubt anyone mentioned:
It is all too often a thankless job-The DM goes through all the time and hard work to make and play a game. Players show up and play...and seem to have enough fun.....but then are just like "whatever" DM and drop some garbage on the floor. All too often a DM will get no thanks.
And it's only worse for the casual players! The DM puts weeks of hard work to create the game. Then goes through the hard work of running the game. Then some casual player just strolls into the game....late...sprawls out on a sofa ..makes jokes on how they "forgot their character and dice" and spill a Mt.Dew on themselves. Then they "play" the game by not paying attention at all and every so often say a gem like "Hey how do I roll to hit?" Then this casual player will say "oh DMs are just players just like me!"
Then, finally, while often no one has anything good to say....nearly everyone will whine and complain. Endlessly....about everything. Players will go way out of the way to attack, insult or otherwise fire negativity at the DM.
Few DMs have the will or ability to be a Hard Fun DM- Well, Hard Fun is my term for the DM that rules the game with a solid foot down and an iron fist. This DM forces the players to do the right things, both in and outside the game.
Of course this is hard in many ways. When your "friend" shows up for the game three hours "becuase they were busy", stumbles inside and drops some d20s on the floor with a "do I hit? How much XP do I get?" Do you invite this jerk in with open arms and just say "sure ruin the game for everyone " Or do you kick this non-friend out of your house and game forever? Well...see a LOT of DMs "can't" do that.
Not to mention when they "interprete" a rule on page 101 and say my sword does 2d20 damage...haha, DM eules says so!" And the DM does not have the will or ability to do or say anything.
Or how a player might say "my character dodges" and somehow think that gives them a bonus 100 to their AC. Then they will whine and argue that they can "never" be hit when they say that.
Or they have the player that does stupid stuff JUST to disrupt the game for EVERYONE. The PCs meet with the baron as part of the plot the other four players want to play through and the other player will be like "I attack the baron!"
Yea, you can "Talk" to such a player....and maybe it works, sometimes. BUT most of the time you really need to be the hard fun DM. And a lot of people are unwilling or unable to do that.