. . . Someone doesn't know the rules well if this is an issue. Since Monks have been a character class forever there's always been ways of enchanting natural attacks to keep pace with magic weapons: Amulet of Mighty Fists. They get enchanted and can be enchanted with weapon effects just like a weapon and can apply them to weapons.
In 3.5 at least a non-humanoid creature would have no issues having a proper magic item kit, they could use most of the generic bonus items, animal Barding was a thing and could be enchanted just like armor, and the aforementioned Amulet of Mighty Fists covered weapons, and since Monks, Animal Companions, and Familiars were things anyway there was always a justification for them being around on a loot table.
The bigger issue is that balancing a person playing an awakened Giant Tiger is actually doing the proper level balancing to make it so that they're not overpowered or underpowered compared to other party members. And those rules are quite complex and difficult to properly implement even by experienced GMs, heck, to this day many people do not actually understand and can apply the Monster Creation Rules outlined in the 3.5 Monster Manual, or understand how Racial Hit Die interact with Class Levels and Level Adjustments. Thing is... these systems ACTUALLY DO WORK, but they take a lot of effort to actually figure out and execute.
Want to know the real reason people didn't get to play those types of things in 3.5? The majority of games took place between levels 1 and 8... going past those levels was rare. An awakened Tiger has 8 HD of Magical Beast and a single level of, say, Fighter, has an ECL of 9... meaning it's considered to be the equivalent of a 9th level PC, placing it above the threshold where most common DnD games were played. And this is for one of the simplest scenarios. If you want to play something like a Dragon, unless you're playing the smallest smol ones, you're looking at ECLs of 15+ really quickly.