The old boxing adage applies to ground work too:
Everyone has a plan, until they get hit.
If the person on Top, for example, is not looking to sub or even get out of position and is content to nail you every time he gets, the ground game from the bottom changes considerably.
The guard is great for sub grappling and for guys that want to get out of it via grappling, but for anyone content to "stay in" and strike, the guy on the bottom will have a horrid time ( understatement).
As long as the strikes ( on top) doesn't over commit and picks and chooses his shots, he can stay in the guard all day and "bomb away".
Now, from the bottom, its far more tricky ( since the guy on top can hot you too of course), hitting from the bottom tends to make you "extend" and sets you up for a mirad of subs and counter strikes.
Typically the guy on the bottom uses strikes to keep the guy on top honest enough NOT to try too many things and the guy on the bottom then has time to work for getting out of there.
Holding the guy on top down tends to be crucial so as to not give him room for striking from the top.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !