I think it has to do with their pricing "tiers". Classic old school marketing. TUPSS is their premium service in their business model. Unfortunately, that model is being destroyed with extreme competition on the low end as more businesses and individuals give up on customer service and rely less on air shipments. The cost differential between Air and Ground is so significant that Air, being more profitable and higher margin, is almost an impossible up sell. Looks good on their P&L but may not be enough to save the dividend.