There were no such bars prior to IIRAIRA.  I think we do not need them.

I don't know where you got the idea that H-2B overstays are a substantial percentage of those here illegally.  Actually, if H-2Bs were easier to obtain, then many of those who come here on visitor visas and then work unlawfully could either initially apply for H-2B status, or could change status to H-2B and work lawfully.  H-2B visa holders must be paid prevailing wages, so that this would actually serve to keep wages higher for all American workers.  

INA 237 has numerous bases of inadmissibility.  I was talking about only one of them.  /surely, you are not suggesting that a suggestion to remove one of those bases is equivalent to a suggestion of getting rid of all of them.