Because they're giant applications that do a lot under the hood that you don't see. Of course you can write your own, we did that during my degree but it was extremely basic.
Thats not that surprising, all games go through this stage of development where you're using basic assets just so you have something to look at while you're iterating gameplay
Lynyrd Skynyrd? Last show I saw of them, they were very much on the trump bandwagon