The question you posed is a great one! I have been in the tech arena now for 17yrs, and it never ceases to amaze me that when it comes to computers, there are those who seem to not be able to understand OS's and really what function they provide.
When it come to giving up on linux, I believe it is because people have very little patience these days, They want the answer right now, and they want to just get in and drive. Linux is not hard to learn, does it have a steep learning curve? That depends on the distro that you use. Naturally if you are new to Linux you would not want to use Arch linux or a strickly command line distro, As you would certainly fail at trying to install and use Linux.
However, the reason's most people give up, really at times gets under my skin, as it really comes down to just being unwilling to pay attention to commands. Linux mint as well as PCLINUXOS are probably the easiest to install. All you have to do mostly is click next, put in your username and password, make sure you are in the right time zone and make a choice as " Use existing drive" then it pretty much installs itself. Once it reboots, You log in and open up firefox, thunderbird for email and away you go.
One of the first things I do is log into the distro's forum and read about the different issues, This way if I have one, I can quickly fix it. There has been times I have had to search for days for a solution, but hey, I have more than one computer, so it's no big deal if the one with linux on it has to sit until I find the solution. If people would stop having unreal expectations on products they have no experience with, or stop listening to windows techs who really don't know anything about linux other than fud that comes from other windows techs would claim to not be able to get it to work or install. If a person who claims to be a computer tech, and cannot install linux or any other OS, then that person really needs to get out of the technical support business and find something more suitable to his inability to learn and follow directions.
Linux is a comon sense OS, as was Novell, Unix and even Apple, They only OS that was built on confusion and as Bill Gates Stated " I am building a OS that would be idiot proof" However I think they actually made it exponientally complicated so the idiot's would be able to click a button and not know what the hell they just did.
And if you think that is scary, just think about all those admins who got certs from reading a book and then being in charge of a whole datacenter of " idiot proof computers" Just ask them to tell you what the command was to hide files and directories in dos using the Attrib command.
anywho, Have a great day!