Yes (formula at bottom of post)

It's because of the amount of tongue weight you require on your hitch to properly and safely balance the trailer you are towing.

When towing, you must have your trailer balanced properly to maintain anywhere between 10% and 15% of the trailer's weight on its tongue.

Here's a demonstration of what incorrect tongue weights will do: https://www.youtube.com/watch?v=w9Dgxe584Ss

Therefore, a 5000 lbs trailer will require at least 500 to 750 pounds of weight on the tongue. That weight on the back of your truck is considered part of your payload of the truck (the yellow sticker on the side of the driver's door.)

If your maximum payload on the sticker shows it's 1500 lbs, then that's the maximum legal weight that your truck can tow before you are towing illegally and unsafely. Contrary to belief, you must also add the weight of the passengers when calculating your payload. Let's do an example:

1500lbs max payload

400 lbs of passengers (2 people in the truck, 200 lbs each)
200 lbs of truck gear (stuff in the back, etc)
100 lbs Tonneau cover (steel ones are this weight, aluminum are 50 lbs)
-------
700 lbs

1500 max payload - 700 lbs current payload = 800 lbs payload leftover.

This means that you can still put about 800 lbs of payload on your hitch.

A 8000 lbs trailer would be 800 lbs at 10% tongue weight. (8000 * 0.10)
A 8000 lbs trailer would be 1200 lbs at 15% tongue weight (8000 * 0.15)

Most experts tell you to be safe, you should do calculations of about 12.5% tongue weight as 10% is a bit too light. Therefore, this truck, with this described payload, would not be able to tow an 8000 lbs trailer safely and legally.

If you wanted to find out what the maximum trailer weight you could tow safely with your leftover payload, just translate the above formulas using algebra. You'd get this:

Max Trailer Weight = Payload Left Over / 0.125

In the above example, we have 800 lbs of payload left over. Therefore, if we wanted to find out the max trailer we could tow with 12.5% tongue weight, we'd do this:

Max Trailer Weight = 800 / 0.125
Max Trailer Weight = 6400 lbs

https://www.readingtruck.com/calculating-yo...owing-capacity/

TL;DR: To find out how much max tow weight you will lose, use this formula:

Payload weight / 0.125 = Lost Tow Weight
A 200 lbs truck topper would be:
200 / 0.125 = 1600 lbs
You would lose 1600 lbs max tow weight with the topper on. Using the same formula, you'd only lose 800 lbs with a steel tonneau cover. You'd only lose 400 lbs with an aluminum tonneau cover.

Obviously if someone isn't towing heavy trailers, this isn't an issue. But I tow a 6500 lbs trailer so I need every pound of payload possible