One of the main reasons to do this is if you are behind CGNAT and cannot port-forward. However, giving out your home IP isn't ideal regardless. If you decide to not use a VPS as a reverse proxy, then you might want to look into using cloudflares proxy, which hides your IP and also serves your content more efficiently. However, I'm not quite familiar on how matrix works so this might not be possible if you need ports other than 80 and 443 as all other ports are not forwarded by the cloudflare proxy.
One of the main reasons to do this is if you are behind CGNAT and cannot port-forward. However, giving out your home IP isn't ideal regardless. If you decide to not use a VPS as a reverse proxy, then you might want to look into using cloudflares proxy, which hides your IP and also serves your content more efficiently. However, I'm not quite familiar on how matrix works so this might not be possible if you need ports other than 80 and 443 as all other ports are not forwarded by the cloudflare proxy.