Its all about price point
retired Jayco sales guy, I never saw a Seneca with air dryer. Price point is what a regional sales rep will tell us sales folks.
I have driven trucks since a pup on the farm in Iowa, not having a air dryer is a disaster soon to happen.
I always recommend to Seneca customers to add on ASAP, better yet put it in the deal upfront. Saves worry and out of pocket later.
Should Jayco have specified one, yes. Freightliner shouldn't even build it without one.
2015 F-450 XLT 440 HP Power Stroke 26.5K Custom Resse F/W, Manual Regen, 19.5 Rubber
2014 Oreion Sand Reeper 4x4 Toy steel everywhere, street legal and licensed, 5 speed manual, 3 cylinder DOHC "Chery" engine and 2 door fun.
2015 Jayco Sesimic 4212 Extreme Weather Package, Dual Pane Windows, Side and rear Patios, 480 watt Zamp Solar Pkg 6 AGM batteries, Residential Fridge, custom Dishwasher, 5500 watt Onan and lot of problems.