But manufacturers don't use it. Maybe they haven't redesigned after the price dropped. Or maybe cause prices is still too high. I think LiFePO4 would be most useful for rack mounts, or small UPSes that aren't possible with lead acid.
Generally lithium UPS win in a 10-year TCO, but SLA wins in up-front costing. Which leaves us with two issues - most consumers look at the sticker price not the TCO, and no-one wants to market their products as "Our lead acid offer only /looks/ cheap, until you see what we charge you for consumables!"
It seems like a fairly recent shift -- heck, the whole solar generator concept is a fairly recent shift -- but maybe it's an indication that LiFePO4 devices are becoming more common in the consumer space.
It has other tradeoffs, though, like being physically large compared to a lead-acid battery of similar capacity (or, say, a bunch of 18650s).
And like other Lithium-based cells, longevity is maximized by never charging it to 100% and leaving it there long-term -- which, unfortunately, is probably not what Ecoflow is doing. (Ideal long-term state-of-charge is closer to somewhere between 50 and 80%.)