As mentioned in previous threads. They don't just say "oh well there's 125/125 on both 1 and 2, lets immediately put 3 on" What they do is that if there is not a 1 person in -> 1 person out every minute or so then they will consider the next server. If people are consistently joining and leaving it makes more sense to only have the 2 servers as it allows whitelisted groups such as police or NHS to not be spread as thin when they have finite members on at one time.
In general, as mentioned above, the search tool is OP and should be used as it doesn't really need this many people to comment when you could find the answer without even having to wait. Regardless, it comes down to admin decisions and they know from stats when the peak times are and when it is best better than you likely will simply because of the data they have available to them. Even beyond that is an admin decision and an admin decision alone so don't expect that they will see this post and immediately turn it on.
Hope this was helpful!