Because all of those vehicles are pushing the limits on range and are stuffed with advanced technology. The actual battery on those weigh about 500Kgs, but like I said, they're pushing the limits of technology. Also all those vehicles have serious performance, which takes big batteries, active battery cooling and heating, motor cooling and so on. All this added complexity adds masses of weight to a vehicle.
For a home made EV, performance is secondary to range, off the shelf components are utilised and there's no cutting edge technology, as the vehicle has already been made. This does make for a comparatively light EV, although range won't be anything like as much as a £50-80K Tesla.
EVs are currently being sold as a designer items or premium products. They're not made on the same scale as petrol engine vehicles, so are regarded as niche items. The price of EVs at the moment reflects that, and this is what is keeping EV sales low.
Hybrids are pointless in my opinion, as they're still petrol powered most of the time.
True but LPG is still a fossil fuel and as such still produces CO2, which will face tight controls in the future, even though it's a way off yet.
