Because he is lying when he said the wait time is only 8-10 years. It is actually more than 100 years.

But, no immigration attorney will ever say that truth to the H1B visa holders from India. I had asked this exact same question to my company attorney 10 years ago and the answer was exact same, wait for 5-10 years.

There are around ~70k software engineer coming to US from India, and everyone of them is told the same lie by their attorneys.

While most of these folks from India wait for their green card for rest of their life, attorneys make a fortune renewing their H1B every year.