Hi shebashetan7
When TC3 was released (TC3 introduced the new steam physics and steam sound system; which could not fully support content made for previous editions), the three sounds by Tony Weber (2 types of 2 cylinder, and a 3 cylinder) were the only steam sounds usable for content for TC3 and newer.
It wasn't till a bit later that a few other sounds appeared, however some of these may not have been suitable for a lot of locos, and may not have been known about by a lot of creators. As such, Tony's sounds have become a defacto standard among a lot of creators and users, in particular as they work quite well.
In many cases, creators will go for a sound they like the sound of, rather than one that is specifically correct to a loco. The steam sound system from TC3+ was designed around supporting this, by basing the sounds on the driving wheel RPM.
Regards