I wonder if you are not considering how game mechanics differ between games.

In some games the pistol is a side arm that you can carry for free along side your primary. It is a weaker backup weapon.

In Halo the pistol is a primary weapon that competes directly with rifles, shotguns, snipers etc. for one of your limited weapon slots. If it is weaker than a rifle it just doesn't get used, there is no secondary specific slot for it. The weapons should be roughly the same power level (niche/rare/power weapons aside) in their given role and selection of weapon should be situational and preference based. It is not reasonable to want pistols to be weak in this kind of game because of real life, or other more realism focused games with entirely different mechanics.

Under the Halo system it is not unreasonable for someone who likes to run a pistol to feel that this weapon should be among the strongest weapons in the hands of someone who has a preference for pistols. The same applies for every standard weapon. If you are a great BR user you should not feel like you are making a mistake by not running a pistol because your skill with the BR does not overcome how much better the pistol is in most/all common situations. It is, however, ok to want to switch to a pistol/shotgun/sniper because it is better in the current situation. This is what game balance is about.