Wrong. Most of a cop's fights do go to the ground, because if we pin the bad guy to the ground, we take away a significant amount of their mobility and ability to resist and fight.the information that i've seen said that that 90% statistic comes from the cops.
When a study was done on street self defense, they went to the group of people who had seen the most fights: cops.
But realize that as a cop, 90% of your fights would go to the ground because 1) you are trying to get the bad guy to get down on the ground
and 2) if he resists you can't (officially) punch or kick him, so it becomes a grappling match
And we can definitely punch, kick, and otherwise strike, when the situation merits it. You won't find many cops kicking very high, for lots of reasons, not least of which is the gun belt... but kicks and punches are certainly in the range of defensive tactics options.