If you wanted to use an old printer, why buy an HP one? Even buying a used one indirectly supports HP. If there’s a secondhand market for HP printers, then they’ll have more value when sold as new. New cars wouldn’t sell so well if their value, rather than only taking a big hit, literally went to zero as soon as you drove them off the lot.

Simply having an HP printer, even a used one, also serves as an advertisement for them. Every time someone visits you and sees your printer, they’ll be reminded of the brand’s existence. Having and using one, even an old one, is a constant minor free advertising for HP.

If you already have an old HP printer that’s working well for you, I wouldn’t recommend trashing it and buying a new one just for the reasons above. There’s environmental concerns to consider. But if you’re looking to buy a used printer, why buy an HP? There’s plenty of other good brands out there that don’t engage is such evil.