This may be your opinion, and it may even be your experience, but it most definitively has not been mine. You also admit earlier that you don't buy TEP, so exactly how did you become the expert on it?
For instance, my daughter purchased a used Palm Pre on eBay. Three months later, the power button went out on it. We took to Sprint and they replaced it free under TEP.
Second, if your phone needs warranty coverage and you don't have TEP, the phone goes back to the manufacturer for repair. No charge, but you get to wait for repair or replacement.
Third, if you have an equipment problem and it is out of warranty, Sprint will repair it for $35, it doesn't matter where you purchased the product. If you doubt this information, I have attached a Sprint handout. Please note at the bottom that there is a $35 fee charged for per incident coverage.
Your experience may be different, but that does NOT mean that this is Sprint policy. You may have just stepped in and "got a free replacement" but most people will NOT without TEP.
Finally, there is nothing stated by Sprint in its handout about WHERE you purchased your phone as to whether you get coverage or not.
Sorry for my tone