Title should say it all, but currently engineer’s grenade kit is the only standard weapon in the game without an auto-attack. I say standard weapon since kits are engineer’s alternatives to weapon swapping.
The closest comparison would be if elementalist’s staff 1 in fire attunement (it’s fireball, if you’re wondering) required ground targeting and had to be pressed every second to attack. Sure, you could just swap attunements, but you lose out on damage if you’re stuck there with all abilities on cooldown.
I’m not asking for all of grenade’s abilities to be auto targeted either, heck, even grenade 1 could remain ground targeted as long as it would auto-cast. We just don’t want more carpal tunnel for engineers. 
Asura Engineer- Aelara Fole