The workers are wrong, then. That is not the purpose of the H1B. Anyone who thinks it should lead to a green card should be barred from getting the visa.
The H1-B is a dual intent status. There are categories that are strictly non-immigrant intent, TN work permits fit this category. Border guards can and do test that you have non-immigrant intent during normal border crossings while under this status ("Where is your home?" "what will you do once your TN is over?").
If it really was intended that H1-Bs not have immigrant intent then there was a legal framework already in place to ensure that. Most likely it is you that is incorrect about the purpose of these H1-Bs.
The "dual-purpose" nature of the H-1B basically means that (1) you are not prohibited to enter on an H-1B with the intent to stay permanently, and, perhaps more significantly (2) you aren't required to leave the US for a period of time after entering on an H-1B before getting an immigrant visa which will let you stay permanently.
But it is still a non-immigrant visa that does not lead to permanent residency or citizenship, but requires you to qualify for, apply for, and secure an immigrant visa if and when you want to become an immigrant rather than a non-immigrant worker.
said by someone who doesn't understand US immigration. H1B is a non immigrant visa, sure, but it can open the door to the immigration process via company sponsorship. I know because I did it, and many others do too. Applying for a greencard from your native country is counterproductive. Basically a 10 year wait for some. Why bother.
If it really was intended that H1-Bs not have immigrant intent then there was a legal framework already in place to ensure that. Most likely it is you that is incorrect about the purpose of these H1-Bs.