Sigh... you really seem to have a hate-on for the Biden administration and "non-progressive" democrats, don't you.
First of all, lets see:
The average income in the U.S. in 2019 was ~$31k. The cutoff is being lowered from $100k to $80k. Which means that the people who are getting cut off have more than twice the national income. Seems to me that if you want to target a social program to those in need, giving the money to people who probably don't need it is probably a waste of time.
Now, will it cost the democrats votes? Yes, people do like receiving money. But:
Biden not following the longtime Canadian tradition of buying off voters will their own money. "Ask not what your country can do for you, ask what you can do for your country" is a dead meme in Canada.