I think the bigger question isn't why shoot the camera through glass, it's why bother with any of this?
It case it's not obvious, I'm experimenting and learning because it's interesting to me.
My audio quality was poor ( noisy, poor quality) Audio generally is more important than video quality for YouTube video. If the subject matter is interesting and the audio is clear, people will watch.
I learned NONE of my cameras have a decent audio preamp.
I tried boosting the signal to my camera so I could reduce in camera amplification, using noise reduction, and equalization, compression etc to make the audio sound better, etc.. I ended up with the Rode Wireless Pro which would have saved me a chunk of money if I had started there. It solved all my audio issues by recording 32bit audio that I could easily sync with the lower quality camera audio in post.
My audio is now noise free and natural sounding, short of my editing out any time I swallow, I'm happy with it.
My Videos were noisy and sometimes out of focus. I was running at higher ISO's because of poor lighting and I had no verification of my focus.
So I added lighting:
1. Replaced my dimmable media room lighting with bulbs that were less warm.
2. Added 2 and then 4 dimmable, color adjustable LED lights that I could match to the ceiling color temperature.
3. Starting playing with my soft box and umbrella.
4. Got a monitor to I could verify focus before recording a whole video out of focus.
Now I was well lit, in focus and my camera running at much lower ISO's making the video much cleaner.
Where I am shooting the lighting was distracting.
So I added a backdrop ( black, white, chromakey green )
Now that the audio and video quality are no longer distracting, the last remaining issue is how well I present whatever it is that I'm presenting. So I'm working on that. Plus I love designing and building things. So a DIY teleprompter is interesting to me. All in I'm at $70 out of pocket plus some PLA and maybe a bit of wood, so pretty cheap fun
All that said and knowing how I tend operate, another question is how long I continue making videos once I have this learning curve pretty well figured out.
I've already started and abandoned a number of videos simply because the effort in post production to make them was far too high for me. I also don't have a dedicated space for video creation, which means that I have to setup and tear down lighting, backdrop, cameras etc.. every time I decide to do something. Now add a teleprompter and the time to fully or mostly script a video and the fact that I'm only doing this because it's interesting and fun for me.
The bottom line is that as I increase my standards and effort required, I make the whole process more prohibitive. I won't bother to monetize my channel because the money generating potential is pitiful and the minute I look at the meager earnings I generated and my time to go into it, I would quit. Like many hobbies in my life, this is purely a passion project.
However, I like adding new tools to my toolbox and I find frequently that knowing how things work helps me gain insight into other things and that at least makes life more interesting and sometimes opens up opportunities.