So I haven't played GW2 for 4+ years and never got very far in it back then but, I've played MMORPG for past 15+ years. Ever since WoW (I dunno if any other mainstream MMORPG offered boost via store before Blizzard introduced them) I always thought boosts didn't have a place for new players.
You should experience the game and hit level cap at least once. Then If you want to level up an alt, and willing to pay for it, by all means.
That being said, I have a Lv80 boost apparently in my inventory, so I assume I got it included when I purchased 1st expansion years ago. It will sit there until I decide to level an alt after hitting cap on my main character.