Why UFP troop convoy not able to protect themselves

[Jason 27]

Many possible first is fact UFP using them during the Dominion war many starship service possible troop make-sift troop convoy simple act better able to war build more effective fighting bigger ship jack of all trade come military needs.

 

Second possible special natural of troop convoy might will design special around deliver troops military equipment that need as will to surface.  Possible action mobile  base means does things starship normal does not do. Or even not have space weapons simple massive sickbay ,combine able carry long troops.

 

Third Possible possible defense limit not match Jem harder ship.

 

Anyone have possible theories