That's because it is. Windows: do nothing, it's already installed. Linux: you have to install.
People compare what they have to do to get Windows on a new machine, which almost always (unless it's an Apple) already has it installed, with what they have to do to get Linux on a new machine, which almost always requires it to be installed. Even the simplest installer will be more difficult than "nothing".
If computers didn't come with any preinstalled operating system, the general opinion would be different.
(That said, most of the "Linux is difficult to install" sentiment is probably either based on outdated information from the time when you had to manually configure everything, or someone who had difficulties because of unsupported or poorly supported hardware.)
I'm more thinking about setting up a new system. Whether it's Windows or Linux, I need to obtain things like an FTP program, a photo editor, a torrent manager, firefox, and so forth. It's a lot easier on Debian than Windows because you can get all of those in 5 minutes from the command line.
Though I was installing from an MSDN install DVD which isn't something everybody would have on hand.
Not just the drivers, but pretty much everything I need for a new Linux system is available through apt. For windows, one must go to a dozen websites, download packages, and click next 10 times in each idiosyncratic install "wizard".
I had a similar experience with my mother, as well – I was constantly having to intervene with tech-support before I installed Ubuntu on her machine.