I agree with you that investment in public transit is preferable to private vehicles in many cases, but the primary purpose of a pickup truck is not personal transportation, it's hauling a bunch of bulky, heavy stuff that isn't feasible to bring on public transit.

Regardless, public transit cannot go everywhere. Rural and light-density suburban areas can never be adequately and cost-effectively served by public transit. Sure, you can run trains or buses into areas like those, but either you'll have excessively low per-route ridership and unsustainably-high operational costs, or you'll have routes that require people to travel several miles in order to get to a station/stop, which means people need private vehicles anyway.

In these cases, you often end up with an overall trip that takes several multiples of the time it would take to drive your own private car. I get that many people might find it acceptable to impose that kind of situation on people (in the name of the environment or whatever reason), but I wouldn't want to live in that world. I use public transit whenever feasible, and only drive when I have to, but there are limits to what I will accept.