Odd choice to use GrapheneOS if you don’t care about security
Not really. People’s threat models differ, some just want to escape Google’s spyware without also requiring your device be a portable iron mountain. Some may also just want the additional control GrapheneOS provides for restricting permissions of apps, or their unique play store handling etc.
GrapheneOS has a ton of positives besides its security IMO.
For me it’s just a little saddening that their secure focus conflicts with extending the life of mobile devices. Although really that’s something that probably won’t change unless we get a truly open source mobile platform, with firmware development out in the open.