In certain competitive environments framerate is definitely limited. Here [0] are the rules for Fallout 4 any% speed runs, framerate must be capped at 60FPS. AFAIK that rule applies to all games in this engine due to physics behavior. I don't follow tournament FPS games, but it wouldn't shock me if there are rules for competitive play there as well.
If you are asking why games like counterstrike don't have limits on online play, that's mostly a commercial question. Would those games be as popular if they limited performance to what was achievable for minimum specs? I certainly wouldn't want to play at 1920x1080 on my nice widescreen monitor, but setting the minimum to a $1500 monitor and the hardware to drive it would guarantee very few players.
If you are asking why games like counterstrike don't have limits on online play, that's mostly a commercial question. Would those games be as popular if they limited performance to what was achievable for minimum specs? I certainly wouldn't want to play at 1920x1080 on my nice widescreen monitor, but setting the minimum to a $1500 monitor and the hardware to drive it would guarantee very few players.
[0] https://www.speedrun.com/fallout_4?h=Any-Full-game&rules=gam...
Edit:typo