The ongoing conflict in Syria has created a new Palestinian refugee problem, as Palestinians (and other minority groups) have been among the most vulnerable and heavily impacted by the ongoing brutal civil war. Refugees have began pouring into Jordan and Lebanon, but both countries' support for Palestinians in other countries notoriously exceeds the hospitality they display to Palestinians in their own borders. Facing an escalating crisis, the UN has asked that the Palestinian Authority (West Bank) and Hamas (Gaza) take in some of their compatriots themselves.
Both refused. The PA's excuse is at least facially reasonable: they don't have any money. But Hamas gives a different reason: rescuing these Palestinians now, you see, would denigrate any "right of return" claims they have against Israel later. I'd say these Palestinians are only useful to Hamas as a bargaining chip against Israel, except that Hamas has no interest in striking a bargain: Palestinians living abroad have precisely one role to play in Hamas' vision of Palestinian nationalism: a human wave to wash away the Jewish state. If they can't serve that function, they have no value and Hamas couldn't care less about them. It's that simple.