Because to do so would mean the Senate becomes Republican controlled and absolutely nothing would get done with Mitch in charge again. It is easy to blame Manchin, who is a wanker, but I blame the American votes for not giving the Dems a clear majority. Look at Maine, they voted for Biden, but then put obstructionist / GOP loyalist Collins back in the Senate.
Objectively look at the Biden's $3.5 trillion infrastructure bill and tell me it's the same as what the GOP would do. It might not pass because of the 50/50 split in the Senate and a couple of ******* Dems, but when 90% of the Democratic Senators support something, and 0% of the Republicans do, you really can't say, "both the same". It's just a nonsense.