Yes and no. Power conditioner do make a difference, I agree. This difference might be quite notable in transparent system, I agree. But in some locations mains power could be "good enough". Equipment with well-designed PSU could benefit from clean power less than other, because good PSU is effectively filtering out mains noise. Some equipment would show no improvement at all. Money spent on acoustics get you a lot of improvements. Money, spent on amps and DACs give you less, but still these are effective upgrades. Changing your laptop for dedicated streamer would give you even less bang for a buck. And only after that it`s time to spend some cash on a power regenerator. A lot of audio enthusiasts would stop at a DAC stage, because people generally can`t afford all toys they want. That`s why power regenerators are not so popular. I would not call power filtering/conditioning/regenerating useless. But it`s neither first, nor even second thing a music lover should care about.