There might be a chance Greece will leave the Euro. But the chance they'll also leave the EU is a lot smaller. Don't confuse the two.
There are political reasons Greece is part of the EU, those will not change.
Also when Greece leaves the Euro Greece will default (the other EU members will not get their money) and the Greece economy collapses even further. After which the other EU members will burn up more money so they can help the sick and needy with aid like medicine, food and other supplies.
Yes, it's strange the Greece economy is part of the Euro-zone and has the same monetary system as the rest of the Euro countries. It should not have happened in the first place because only similar economies should be part of the same monetary system otherwise you can't use the currency to at least have some control of your monetary system.
But I'm not so sure GrExit really is a great solution. Because it won't give the creditors their money back. And the current austerities are already the cause of death of certain people in Greece right now, let's not make it a lot worse.