Right now Texas claims to have far more ventilators than it needs according to most projections. If it loans some out and needs them, they'd still wind up saving more lives than they would otherwise.
A lot of states that have furiously asked for them probably have too many. California, complaining it hadn't enough, is sending some. The reports said that they were generous (yes, they rather were) but could do this before the "crush" of cases hit. The "crush" will be in a week, and if people go on those ventilators tomorrow they won't be freed up in time to be sent back. California, in other words ran the numbers and decided that the numbers for best case + reasonable cushion were far lower than inventory. Then they could sit there on unused ventilators while some places actually ran short or at least cut it very close.
A lot of peak usage dates are 2-3 weeks apart, meaning that loaning is possible, provided that patients aren't good for staying on them for weeks and weeks. That will end badly--and while the ethics of terminating life support are bad, keeping somebody intubated weeks or months, sedated or conscious, with no real hope of improvement ... No better.