That's a good question. I suspect in this case it's a matter of Tesla having a large supply of a certain kind of cell at low cost, so that's what they used in

That's a good question. I suspect in this case it's a matter of Tesla having a large supply of a certain kind of cell at low cost, so that's what they used in Powerwalls. If someone else can make a product that is cheaper, safer, and lasts much longer by using LFP cells, then there won't be any reason to buy Tesla's product. In the long run I expect LFP (or whatever supersedes LFP) to win in the end. I don't know if there are any LFP-based Powerwall-equivalent products, but I assume they must exist at this point and are probably being deployed in utility power storage projects. I just don't see why you wouldn't use LFP unless you either can't get them for a reasonable cost, or these things are being deployed in unheated facilities that experience below-freezing temperatures (LFP generally can't be charged in sub-freezing temperatures).