Whatever I write about this on here, people argue with me, but you can have an ICE-only Gen1 Insight, still have "adequate" acceleration, and get better fuel economy than most cars. The Gen2 Prius traction battery weighs 117.5 pounds and the Gen1 Insight one weighs 65 pounds. If you disable or remove the battery, the electric motor and other components become useless. The Gen1 Insight weighs 1,847 pounds and the Gen2 Prius weighs 2,903; if ten percent of their weight was the hybrid part, it would only cost around five percent more fuel to move it.
The other point that people have not mentioned yet is battery replacement. According to
Toyota Hybrid Battery Replacement Cost Guide, the average cost to replace a First- or Second-generation Prius battery is $2,299. You can get a Civic HX for that price and I have had 50-MPG tanks, but the traction battery would last a couple of times as long as my timing belt.
Wouldn't it, Old Mech?
That same page says that people almost never need to replace hybrid batteries, but I see Prii with worn-out batteries on Craigslist all of the time.
Then there is the "Out of my way! I am saving the world!" phenomenon.