The fact that not all criminals get caught does NOT mean that all laws don't get enforced. Learn the difference between the two.
Furthermore, just because you love the idea of people flooding across our borders with little to no oversight or control does NOT make illegal immigration a "lesser offense".
And finally, who told you that being arrested for illegal immigration - or any other criminal offense - precludes getting an order of protection? You DO realize that people in law enforcement custody do still have access to the services of the legal system, right? A judge may decide not to issue an OOP if the plaintiff is going to be deported, since the OOP would be unenforceable outside the United States and therefore a waste of time, but he also may issue it if there's a chance that the plaintiff is going to remain in or return to the United States. Either way, she still retains the right to petition for it even while in custody. The two are not mutually exclusive.