Why can't U.S. Presidents use their own money?

It's supposed to discourage corruption. Eg, some foreign governments try to hbribe Trump by staying in his hotels.

Presidents do not "go shopping," so they don't need cash or credit cards on them. All their assets (except some home furnishings they have brought to the "family quarters" rooms in one wing of the White House) go into a blind trust. This prevents any presidents from taking any sort of action which could favor a particular investment they may hold - they no longer know what investments they hold. Buying, say, Christmas gifts for family? It's billed & goes to managers of the blind trust & financial accounts for payment.

Except for Trump, who donates his salary quarterly to various charities, since he has extensive assets to cover any personal expenses, other presidents have their bills paid by accountants who handle the First Family's financial affairs, taken out their salaries. This bill payment system includes things such as personal travel. So taxpayers actually do not pay presidential flights "home for the holidays," or to their favorite golf course, etc. It's all billed back by WH staff & paid out of personal funds (or salary). Obviously, someone who has a lot of personal assets when entering office can readily do more travel - or whatever - without worrying about high costs coming out of salary.

Trump gets a lot of flack, but remember, he licenses USE of the Trump name on properties he developed or partnered with, and he does not actually own things like Trump Tower (he owns a condo in this condo-development).

Another consideration: Presidents are supposed to tend to official business, not spend time paying bills, reconciling checking account, etc.

president don't have all those things taken away.

Presidents have to pay for quite a lot of stuff while they are president, including the food that they and their family eat.

That just isn't true. https://nypost.com/2019/09/19/trump-says-he-keeps-...

In the past Presidents have either sold their investments or put them in Blind Trusts so there is no obvious quid pro quo that favors the Presidents businesses or dealing.

Trump said it was not a law and he was only going to hand over "day to day" to his sons Jr and Eric.

He still profits from his business and obviously has at least $20 in his pocket. Presidents don't drive themselves on public roads or need cash, they have people for that.

Trump is abusing the office to use our money and to get richer off of it.

It is to avoid even the possibility that it could look like impropriety. If the president paid for something and then there was a scandal with that then he'd be tied to it even if it was completely honest.

It also saves him from ridiculous scrutiny. For example, if the president tipped waiters, the left would be checking every penny and if he tipped a black guy or woman, or gay person one penny less, they'd scream racist.

There's lots of other examples, infinite really. If he bought a hammer and it was manufactured in China...scandal. if he bought something from a bakery and then later that Baker refused to bake a cake for a gay wedding...scandal. If he paid his friend the Gov of VA for a baseball card and later that govenor was in blackface...scandal...

That is not true.

Heads of state normally do not spend their own money while in office and usually do not carry cash or cards. However, US Presidents are not somehow prohibited from having cash or cards.

This Quora answer does a good job of explaining.

https://www.quora.com/Does-the-US-President-carry-...

I have never heard that those things were taken away. Do you have a source for that? Edit: After a quick search I have found that your assertion is false.