I think Tailscale is popular because of how plug and play it is for most people. Although the main reason I use it over self hosting wireguard is the NAT busting it does, which has so far worked flawlessly for me with no setup aside from installing on both devices. There is nothing wrong with self hosting wireguard, but it doesn't actually do the same job as tailscale.
as someone who uses tailscale: exactly this.
i have my homelab only reachable via tailscale and can access everything i would ever want on the go that way. it was a matter of 15 min to get it all working.
NAT busting is a great point.
Wireguard by itself also doesn't allow for 2FA or expiring keys. Not as relevant for private use, but some orgs need it for compliance. The idea was always that things like that need to be implemented by an application on top of it, so you end up with something like tailscale eventually.