Tax filings by illegals are up big time - there are plenty NOT demonstrating who will do whatever it takes to get that chance - anyone who doesn't want to can leave.
Those who wanted the chance for American citizenship should have applied for legal entry. That's the law.
What does filing taxes improve their standing? If they enter the country illegally and then use false identification in order to get a ss#, and then use that falsly acquired ss# to file taxes and get a refund...how many more laws have they broken?