For starters, you have to atune before you can port and the airships are the quickest means for intercity travel. Next, gil is an issue for some players. When I joined, one of my FC mates offered to give me a million gil, and I refused it because I wanted to learn how to acquire it on my own. Many players would not do the same and take the gil, resulting in never learning how to acquire their own funds and struggling when what they want/need is out of their means. Kind of like throwing a zoo animal into the wild and expecting it to know how to hunt for itself.

Next, gil rewards are very minimal in the beginning, I definitely remember not having the luxury of porting liberally like I do now at lv15 when I got access to airships. Nopee.

Then you also have players like me, who hoard gil lol. I still take airships to the related city of my objective for the cheaper ports all the time. The difference in time is definitely not worth what you save in gil lol. We're talking seconds opposed to minutes. Not to mention whatever objective you're doing will likely replenish the port cost. So I obviously take them for another reason. It's a nice little break to check the notifications on my phone