why cant i use credit card & debit card to purchase a truck

The biggest difference I hear about a paid off use truck or buying a new one is who you want your money going to (dealership or a mechanic shop)

 

$2000

 

And for any bigger repair, maybe 5 large and up, they're going to want half up front.

 

That's exactly how I'd operate when I get a shop open. Every independent I know that failed, failed because they carried too many guys on credit. The successful ones wanted payment up front. At a bare minimum I'd want parts paid for up front. At least then I'd only be out my time if they didn't cough up the cash.

 

No. I don't know about all shops, but Freightliner is $2K max on a credit card.

Don't even consider doing this unless you have $20K in cash for a rainy day, after you purchase and register the truck.

 

When it comes to large(over $10K ) cash transactions, there are a myriad of banking regulations that prevent them from being completed, for logical reasons. All of them have to be reported.
If you have the money in the account covered by the debit card, an electronic funds transfer is what most dealers/banks/ etc will ask for. Cash will be turned down in large amounts, and the dealer can get in big trouble for ignoring the rules.