I'm not against trucks. But on the scale of cool things to add to this sim trucks would be the last on my list. Trucks have WOW factor, "oh my god wouldn't it be fun to race trucks! WOW!". While people have already suggested truck racing umpteen times, karts, muscle cars, rally, dedicated drag cars, can am, historic etc have more support, are more popular and would be better suited to LFS. Many suggestions also for more class based racing. I don't know how many more cars people expect LFS to get in the future, but I predict that not all of these choices will come to light. So considering the workload on Eric and Scawen to model and code new vehicles in the future I'm hoping that trucks don't get in the way of many other suggestions which are perhaps less novel, less WOW! but ultimately more relevant to the sim and have their roots planted more deeply in motor racing history. Jet boats would be enormous fun too, but I wouldn't support those in front of the humble kart, for example.
So some people may be very happy suggesting trucks, Im just as happy to unsuggest it. It's just my view.