Scope and variety. Stay in the industry long enough and you’ll get opportunities to drive so many different types of vehicles. Opportunities to work away or work locally. Consider all the peripheral occupations, from working in the traffic office, garage, warehousing, management, training. I’m fortunate enough to have done a bit of most of these but found my niche in training. It wouldn’t suit everyone but I only mention it because there’s a lot more to the industry than driving alone - much as I thoroughly enjoyed that as well.
The scope of the industry is huge and there’s something for the majority of folks.
Pete 