You have genuine concern Paul and a good observation. I was just talking to someone about this very thing, but hopefully your concern is the point of your reel: what you will sound like if given the opportunity to do so. A large majority of jobs, you will be providing the voice. Your voice should sound good wherever you are recording it, with whatever background noise or music is added. If it doesn't, you as the talent needs to revisit what you are using for a home studio.
Even people with home studios will be connecting with CleanFeed or SSI initiated from the engineer. Your voice is basically going to the great studio with the quality gear. It's for jobs like this that demo reels shine.
For jobs with less mastering, or different needs, such as audio books, that's a different reel altogether, and a different topic.
if your demo reel is making you sound so different, again, the Voice talent might need to revisit what is used as a home setup. We still do professional work from home. We are also not all trained engineers, but covid has certainly forced us all to re-evaluate what we need to do as voice over artists. Some people are even lucky enough to have friends or associates who are engineers who can help. Hopefully you will discover that most of us would be able to do quality voice demos from home if we had the mastering experience, the scripts, the music and the voice. Well, we have the voice. The reason we go to professionals to get our reels done is they should have the other stuff. If they came to your home with the stuff, you could probably do it there. it might just take a little longer. The big catch word there is "experience". You need a proper engineer to master your demos. Someone with a good ear. If you're good at it, awesome. Myself, I've been doing this thing for over 20yrs. I'm awesome on one side of the mic (ahem... cough) but just scratching the surface on the other. I don't have the master experience to do myself justice. I deserve a better reel than I could give me.
As I mentioned to April, your reel is your electronic business card. It gets you in the door. Once you are in, it's up to you and your talent. And luck. and hard work. and the position of Venus.... so many variables. Once you book a few jobs, you take your best of and make a Showreel. then your demos will sound exactly like what you sound like, because there is the proof.... actually jobs using your voice. Some from studios, some from your home. In the end, your demo is to get the potential client to hear your voice. Wrapping it in a nice package doesn't hurt.
It is a genuine concern, but hopefully, one in which you can look at your own studio space and ask yourself, if I had the skillset, could I do it from home? Can I provide professional sounding VO from my home studio. If the answer is yes, job done. Demo reels are present to yourself. If the answer is no, find out why and sort it. It's why we call plumbers, or take our cars to the garage. we go to the professionals. If we had that skill and the tools to go with it... you see where I'm going.
Again, I will say, if you think a studio demo has you sound nothing like you would from your home studio, for most of us, I think we are just lacking the skills (and a friend with a honest ear).