The Crawler goes back to the days of Tiberium Sun Firestorm. There it tended to be seen as a mobile structure to build fighting units, and there the units protected it, plus the player had to be more carefully in regards to its position regarding the enemy.
The modern version by adding a weapon plus other features, the modern Crawler could be used alongside fighting units to compliment them. BUT still the player has to be careful plus also have skill in using it in that role along with their other fighting units, this also within their team when playing multiplayer team games and that also requires some skill to function and work as a team by each team member.
Anyway, here is an image from the start of a mission in Tiberium Sun Firestorm, where players deployed their early version Crawler and then went hunting harvesters as seen below.
