Its not someone. Not you or me. Its banks mainly and funds. Its about liquidity. Banks dont keep depositor cash they lend it out. They also own treasuries. They borrow cash from the FED and use their treasuries as collateral.
"Classified as a
money-market instrument, a repurchase agreement functions in effect as a short-term, collateral-backed, interest-bearing loan. The buyer acts as a short-term lender, while the seller acts as a short-term borrower.1 The securities being sold are the collateral. Thus the goals of both parties, secured funding and liquidity, are met."
Taper is only theoretical because we no longer have an independent Fed. They should have tapered last year but the Market puked as soon as it was mentioned and Janet Powell said "Oops, just kidding".