7-08 is as suitable as any other chambering in its class and is as good as the the person behind the trigger.
I reload for 340WBY, 300WBY, 6.5-284, 223, 44mag. I have in the past have reloaded for 30-30, 7.7JAP, 308, 9mm, 45ACP, 300winmag, and 7mmRM. The WBY's and 6.5-284, along with 7.7JAP almost require that you load your own. It's not necessarily because of the expense of the ammunition, but the selection of available ammunition.
While I have never owned or even shot 7-08, it's as viable a chambering as any other cartridge in its class. The 51mm case is about as efficient a choice for medium to largish game as is available to the shooter and hunter.
I have a soft spot for 7mm , the first magnum rifle I owned and reloaded for was a 7mag I started reloading for in 1976. Along with 7.62, 7mm offers more bullet choices than any other caliber that I can think of.
It could be that its popularity with your friends is that it works and works as well as any other chambering available if your willing to load it for yourself.
So, people use it because it works and works well, with out being over powered or expensive to reload for.
Brass is easily obtained especially if you are able to to slightly reform 308 brass.
Some shooters, including myself enjoy shooting obscure chamberings, just like some people enjoy driving antique cars. Personally, I have an interest in grossly overpowered cartridges, as well as grossly overpowered cars and women.
7-08 could be considered as being in the Goldilocks zone of cartridges, not too fast, not too slow, but for some it's just right.