It's to help new players. A more worded and descriptive description helps when you first use that card or see it used. 5/(permanent symbol) is rather different and could be potentially confusing. It has five attack and then a symbol for HP? That doesn't correlate with the rest of the game. Even if all the weapons were like that.
Some can be worded better, like your tower suggesting.
And for some abilities to just have a name or a symbol is a horrible idea, no offense. It's completely deterring for new players. More experienced players like us would know them easily, but new players wouldn't have a clue. They'd have to either understand it through seeing it played, or just experiment for themselves. Even if there is a pop up window or something that would explain the ability, having the description of the ability on the card is best and more user friendly.