The point is that the desire to use a OTP typically hinges on it being "uncrackable". By using a PRNG (even if it is a cryptographic stream cipher) to generate

The point is that the desire to use a OTP typically hinges on it being "uncrackable". By using a PRNG (even if it is a cryptographic stream cipher) to generate your pad, you've just re-introduced the same "crackability" (by way of the PRNG), and your system is strictly worse (same security, worse logistics) than an existing system.