If you're coming from a low income country and are in a life situation where you're willing to put up with worse living situation and more restrictive workers rights for a while to put aside money and then leave, coming to the UK is still an opportunity, so it's entirely unsurprising there's still a net inflow even though a lot of us are either leaving or considering it (I have family here that'll keep me here for a few more years, but once my son is no longer living between mine and his mums I likely won't stay long).