I assume the reason why it isn't carpeted is the same reason why there isn't more seating available.
The alcoves are nowhere near large enough for the number of passengers going through the station at any given time. I might be misremebering, but at times the alcoves are only for priority boarding or business class boarding, and economy have to line up. Someone else is free to correct me on this, but there's no real way to check and/or gauge access to the alcoves, so anyone can sit there. Occasionally staff will come around and scan tickets if a train is boarding soon.
There is a public address which IIRC can be heard in the Great Hall, but it's not amazing. It's a cumbersome station due to the layout of the main VIA Hall, the alcoves, and the escalators, which staff will typically either guard or block off in some way, as people cannot simply go up to access the platforms similar to how the GO platforms can be accessed. There isn't enough room for passengers to queue and wait on the platforms themselves.
Are you catching a common theme yet?
One latest gripe is the location of the new Tim Horton's in the VIA Hall. Instead of being located in the Hall behind lines of people it should be located in the Great Hall on the side where the former ticketing offices used to be. It would provide a general retail option for people cutting through the station, would provide some kind of purpose to the Great Hall, and would free up whatever space the VIA Hall previously had. I'm sure there are rules against it.
In general, Union is a rough station because there's no real way to gauge to see where your train is or what its status is on the platform. There's no easily identifiable gate or door (they're hidden behind the alcoves) and so unlike an airport or, say, Ottawa, you can't keep an eye to see what's going on with boarding. Combine that with being an incredibly busy station of trains arriving and departing. I typically try to arrive as close to my departure time as I can as I hate spending time in the VIA Hall, and the business lounge is located far enough away that it takes a few moments to get from there to the gate. This is in contrast to the new lounge in Ottawa where I will gladly show up ~30 minutes in advance as it's a nice spot to hang out in prior to boarding, and is located directly next to the gates with views of the trains
All of the improvements to literally everything else at Union have been very good
except for VIA boarding and Hall.