To start with:

Aurelion Sol has some good harassment in lane, as well as good roaming, so playing Aurelion Sol is a good option if you need some magic damage on your ream, or you just want to have pressure on the map as well a s on the lane.

The reason why I started playing everything as a support, is thanks to the new items on season 10, which let us have a lot more options, like Kled or a better option for Ashe, but with Aurelion Sol you still have the option to play as a carry champion, an initiation champion or a peel champion.

Some of your benefits with Aurelion Sol are:

You can initiate and peel thanks to your Breath of Light and Falling Star making things easier to your team, and adding Rylai's Crystal Scepter with your Astral Flight it's even more simple.
You can roam a lot thanks to your Singularity and you have some good DPS thanks to your Astral Flight so taking objectives like dragons is easier.