I'm not sure I accept your premise - there are tons of vehicles with street-side kitchen layouts. Everything from the classic Volkswagen Westfalia and Sportsmobile Westy, to most slide-in truck campers, to every Earthcruiser I've stuck my head into has had the kitchen on the left/driver's/street-side. "Campground" RVs very often have the kitchens on that side because generally the US RV industry has standardized on the street-side being the "utility" side of the camper - electrical and water hook-ups tend to be on that side, so having the galley there means that plumbing runs for pressurized city-water are short, as can be the corresponding greywater drains. Freshwater tanks can generally be located wherever is convenient (and weight distribution should be prioritized for an overlander).
There's a certain common design pattern in the Revel/Storyteller/other-large-class-B segment that puts the kitchen on the curb-side, for sure. For those models, the cynical side of me says they're selling the dream of "gazing out at beautiful vistas with the slider open while you make your morning pour-over". The slightly more practical side says that putting the kitchen on the curb makes it easier to vent cooking smells/aerosolized oils/etc to the big side door and co-locates some of the supplies like water/gas so that they could be accessible from both inside and outside the camper.
If you're building your own, then just think through how you will use it, and optimize it for your needs. I would urge you to prioritize usage over construction simplicity, if only because you'll (hopefully) be using it for much longer than you'll be building it, and I'd rather make sure my time and energy is frontloaded so that everything is easy and enjoyable when I'm in the field. If an extra couple feet of plumbing will make your life better a year from now, probably worth it.
When I built our first campervan, I used a hybrid "weekender/westy camper" layout. I did not have a fixed closet or full galley, but I did build a cabinet on the street side in order to locate the fridge and a butane stove for making coffee (and very rarely making food inside). I put the water access on the curb-side (sprayer only, no sink), because I did more cooking outside than inside and that's where it was most convenient. In our newer rig (4WC flatbed Hawk), the galley is on the street side (see above re: "normal" RV construction), but the downside is that when cooking outside, it's least-convenient to access the kitchen if something is needed.
TL;DR - there are practical considerations for some builders, but put your kitchen wherever it will work best for you in the long run.