I've had a Google (Voice) number for... hard to even say now, 8 years? And i.. well, i think i've only gotten a few calls to that number, ever.
In fact, i have a normal cell number (i don't link my google and cell provider numbers), and i get texted spam to it maybe twice a year, but i can't recall anything really.. ever, to my Google number.
To my knowledge i don't have any anti-spam settings enabled on Google Voice (though, they do exist). I wonder what the root cause for this is?
I often forget that "in this day and age", call spam is still an issue.