why or why not?

I am asking if there should be a national sales tax implemented instead of the current taxing systems. and why or why not?

I will first assume that you live in the United States of America and that you mean in real life.

Why: simpler to collect. Effects all purchases equally (by percent).

Why not:

Rich consumer drain: go to Vancouver, Seattle to see this in action. Many (maybe even most) people who make significant purchases do so in Portland across the Columbia river, why? No Sales tax. Completely legal tax haven. This effects those who can more easily go to another city to buy things (middle income and above) and those who make purchases large enough to justify doing so (high middle income and above) the most.
Now, sure, if we had a national sales tax, including an internet sales tariff, not many people would just go to Canada or Mexico to buy something, but the rich would gladly spend a few thousand dollars and a few hours on a plane in order to get that new Porsche from Canada instead of paying $30,000 extra to buy it here. Now not only didn’t they pay any taxes on it, but they didn’t even stimulate the economy via making a purchase. Perfect, they can live here for free without even buying anything here.

Wealth-oriented Business drain: similarly, the wealthy wouldn’t even be able to find a new Porsche here. Porsche wouldn’t find it economical to try to sell cars here, especially with the import regulations that are faced in the U.S.

The rich spend more on services: right now, services are taxed. If we tax goods instead, then the wealthy will just pay for services even more than they already do. Sure, this means that some of the poor can be employed as nannies, guards, maids, cooks, etc, but it also means that the rich will have a lot of leverage in society, more than they already do. They could be earning a lot and buying a lot in the way of services, but they wouldn’t be paying taxes. Essentially, unless you also dramatically increased the minimum wages, you’d end up with a few millionaires and lots of servants. Not great for the middle class.

Small-time informal sales of goods are extremely hard to regulate.

Small businesses need to do more book-keeping in order to keep track of sales tax.

Technology will suffer: if people only buy a new laptop every 4 years instead of every 3, there will be a smaller market of people buying laptops and everyone’s laptops will be older. Same goes for really any purchasable improvable items.

International trade will suffer: we won’t be able to sell things as easily because people have to pay our taxes to buy things here.

Tourism will suffer: for the same reason.