I'll paint a scenario in which people have lost very large amounts of Bitcoins. This is how NOT to do it:
1. Import your paper wallet into a wallet
2. Send a small transaction
3. Delete the wallet assuming the remaining balance is still on your paper wallet
4. Realize you've lost thousands of Bitcoins and will never be a crypto millionaire

It depends on the wallet how change is treated, but it's safe to assume change will go to a different address and not back to your own paper wallet, unless you take precautions!
That's why it's better to sweep the funds into a wallet (make sure you create a backup of the wallet before funding it!), make payments from there, and send remaining funds back to a (new!) paper wallet if needed.

Further reading: Five Ways to Lose Money with Bitcoin Change Addresses