It's expensive and so is the ammunition. It's a heavy rifle and the recoil with the high pressure ammo is pretty stout. This is not the gun to be issuing to female troops on a general issue duty rifle.
As much as it pains me to confess, the M16/M4 family of rifles is arguable the best military rifle in the world.
Light weight, points better than any rifle ever made and is very accurate and very shootable .
The last 25 years have seen billions of dollars in the military and private sector invested to refine the M16 weapons system to the most accurate, reliable, effective and flexible rifle ever made.
The proliferation of a multitude of upper receiver configurations means one rife can span the range of Short barreled CQB weapons, Issue carbine, Designated Marksman Rife/Special Purpose Rifle , 22 LR rim fire inexpensive training rifle. It takes less than a minute to convert from one configuration to the another and you are good to go.
These uppers can use special purpose ammo like 300 Blackout and others to take up the slack when 5.56 X45 is not the optimum solution to the task at hand. Most are capable of using existing M16 magazines.
Most of it's competitors are a refinement or enhancement on the basic M16/M4 system and, while they may improve on the M16 is some areas, very few have been able to match, much less show an overall improvement, the overall performance of the M16/M4 weapons system.
Almost all do so at at a higher weight, more complexity, more bulk and reduced maneuverability.
Bull pup configuration rifles have many advantages over the M16/M4 and it's competitors but they are different and require much retraining over the conventional rifles and many users just prefer a conventional configuration.
The Sig M7 will most likely find a welcome place as a high power DMR/ SPR to give a squad a major upgrade in capability while the rest field M16/M4 variants using an intermediate power ammunition. The feed back from Ukraine pretty much supports this philosophy of use.
From wiki…” XM7 rifle weighs about 2 lb (0.91 kg) more and each soldier carries roughly a 4 lb (1.8 kg) heavier load with 70 fewer rounds.[3][19]”
This is exactly the goal for anyone signing a long-term govt contract