Whereas with a TV, everyone knows what a TV box can sustain and can’t.
Why should the underpaid and overworked handler care? In the US, handlers at hubs earn minimum wage and are expected to process a certain number of packages per shift - so they may not provide the care you'd expect. Drivers earn more than minimum wage, but still are pressured to deliver quickly - so packages get tossed a lot. The handlers incentives are not aligned with the shippers - and this for the unionized courier (UPS) - I imagine FedEx and DHL may be more demanding on throughput.
Even if they don’t they will likely learn that televisions in boxes are fragile sooner than that they learn that about bicycle frames, as they’ll handle a lot more of them.
I also suspect most televisions crack sooner than bicycle frames.