There's a lot to be said for the AR15 for progressive rifleman/hunter who likes owning multiple calibers and yet doesn't want a half dozen hunting rifles in his safe that he'll only use once a year when he can own an AR15 that he'll shoot year 'round.  If he has an AR15 lower he can have multiple uppers in different chamberings as well as different barrel lengths, all mounted with different optics for different game and different hunting seasons.  He might be able to put these all together with one bolt or he might need a couple of fitted bolts of different sizes.  And contrary to some expectations that one needs an AR10, which we usually think of as a .308-size AR compared to the .223-size AR15, many larger caliber rifles can be built on the AR15 size rifle and don't require an AR10, which of course is a larger rifle--meaning a completely different lower. 

Remington has actually been at the forefront of the AR15-as-a-hunting rifle with their R-15, which comes in .204 Ruger, .223 Remington, the .30AR, which is very good .30 caliber deer cartridge, and the .450 Bushmaster, which is a powerful big bore.  Of course Remington also offers their R-25, which is an AR10-size rifle available in .243 Winchester, 7mm-08, and .308 Winchester for those who want the large size rifle. 

But Remington just offers the tip of the iceberg, and there are dozens of chamberings that can be had with not much hassle and not very expensively compared to buying a lot of separate hunting rifles at $750 to $1500 each these days.

And really, doesn't this look more like a hunting rifle than military weapon?  They're not all "black rifles" anymore.