Seems to me 'dead' for a taxi isn't 'dead' for a static power bank. If I'm running a taxi I've got hard limits on how large my battery can be and how heavy, and I want to maximise the mileage I get between charges, because while my taxi is charging it's not out on the road earning money. When that battery is keeping only maybe 80% of its original design charge, and now I have to schedule one recharge too many per working day? Bang goes my business plan, so I'm replacing it.
If I'm storing energy for the grid I'm a lot less worried about that. It only stores 80% of what it did when new? Better than nothing, and the taxi firm is selling them off cheap. I'll stack them up!