despite ubuntu being damn close the gap isnt closed yet.
Ubuntu is not close. There's still a big gap between Ubuntu and Windows. And it's doubtful whether this gap will ever be closed.
1. Software installation - people are used to going to a software company's site, downloading the .exe and double clicking. That's all they have to do, that's all they want to do. People would have to retrain themselves to go to a package manager or even - gasp - learn some terminal commands. And what if the package they want isn't in the repo? Then what? Is one going to teach them how to add a PPA or install the dependencies to get their .deb running? By then they're already bored and screaming to go back to Windows.
2. Gaming. There's still a huge way to go before Ubuntu has anything like the compatibility of Windows. Proton goes some way towards solving this, but only some. There are still loads of mainstream games that don't work.
3. MS Office. It is vital to MS that they retain their position as market leaders. Libre Office is good, but it falls over in its compatibility the more you try to do with it. Ever tried creating a Libre document with loads of graphs, tables and footnotes and then opening it in Word? It'll get messed up. This will likely never change since MS will always switch things around to
ensure incompatibility. If Libre were 100% compatible with MS Office, why would anyone use MS Office?
4. Stability. Ubuntu is still too easy to break if you don't know what you're doing, especially for newcomers. Impatience, entering the wrong terminal commands, installing things wrongly can all contribute. The first time I installed Ubuntu I broke it twice, I don't even know how. Linux gives people more control and more power than they're used to or understand, and for many people, this can be a bad thing.
5. Compatibility with other software. My wife uses a particular piece of software which is vital to her work. This does not exist in Linux, so it fails out the gate for her. How many other pieces of software must this be the case for? One dreads to think.
In short, Ubuntu is great for people with an interest in Linux, who are learning, whose work is not hampered by it, who have made it work for them and/or who have come back from more advanced distros and want something that just works for their use-cases. But for a lot of people it just won't cut it.
There's simply too much choice. I've lost count of the number of times I've seen threads all over the place asking what distro to use where the answer is "the one that suits you the best" or something like that. Without trying them, nobody knows what they like best.
I think I downloaded and tried upwards of 20 .isos till I found the two or three distros that worked for me. And then I had to learn them. Very few people have the time or inclination to do that.