First of all your wrong, and it has nothing to do with extending their stay. It is about Residency and it is a form of amnesty.
These aliens are in this country illegally. If they wished to apply for Residency, by law, they would be required to return to their home country and apply for the visa.
In their home country, they would be required to pass a criminal background check of their record in their home country and the US.
Under 245(i), they pay the $1000.00 and bypass the home country background check, and the US background check is done by some clerk, not a Law Enforcement officer.
On top of that, 245(i) was originally removed from the 1996 INA (Immigration & Naturalization Act) because of the fraud that in propitiates (marriage fraud being the largest).
It also send to wrong message to those that are legally trying to immigrate to this country.