Because it factors into which ship you are going to buy/use. Every ship needs pros and cons to make that decision. Games need limitations to overcome, games need balance to make the decision relevant. You need to do a particular job, this defines your options for a ship. Without balance there's 2 ways to go. You either always go the the OP ship, or when all ships become jacks of all trade, you lose the gameplay mechanic.
It's not just combat situations where the need for balance kicks in.
It's not just combat situations where the need for balance kicks in.