I don't think that piracy is relevant to streamed media.
piracy | ˈpʌɪrəsi | noun 1 [mass noun] the practice of attacking and robbing ships at sea.
I'm not at sea and robbing the ship called 'You Tube'
• a practice similar to piracy but in other contexts, especially hijacking: air piracy.
I'm not in the air or in any other context robbing anything called 'You Tube'
2 the unauthorized use or reproduction of another's work: software piracy.
Am I unauthorized? I do not seem to have any message telling me this. You Tube and Google content likes to introduce 'free' services and is how such corporations have taken public utilities like the internet and made it synonymous with their services, DNS, search etc. This should really not be the case. The internet was designed (or at least purported) to be an open public service for the utilization and benefit of the general public. This is not unauthorized. If they are unhappy, and want to tell me they are unhappy because themselves, their ad partners or content creators are not getting what they want, then they can create subscription only access, like other platforms.
Like Louis said, streamed media is either pay-to-view (with subscription, content is payed for upfront) or it is not asking for a subscription fee. At least that would fit into the definition above and what may constitute piracy.
If media is not asking for this and trying to create a round about way of monetization of streamed content. Avoiding adverts is not piracy or hijacking of any service. I would do the same along with the majority of TV views when there is a commercial/ad break interrupting some kind of programming/content.
Re Piracy.
I remember when we would record TV on VHS tapes or maybe radio to cassette tapes. In a similar way, laws are becoming 100% ridiculous to ask that consumer devices (i.e. technology) is designed with a specific use case in mind. Like, yeah, you might not be happy if someone was redistributing a work without royalties or zapping content, but you have to accept that the digital domain and the consumer electronics industry allows for people to do such things with considerable ease.
Instead of trying to outlaw anything and everything concerned with the saving, copying, sharing deleting of data, why not just try to adjust your business model to one that actually provides value and then people will be willing to pay for?
.. like @nym said, there's more than one reason to block ads. I do not wish to lease out storage space on my device to a gang of companies and their third-parties who feel like surreptitiously collecting information about where I go and with whom I liaise.
This is akin to promulgating a technologically enabled lifestyle through consumer devices and then stripping away the benefits for it to the end-user, or simply a digital panopticon. A technocratic faction of fascism.
I'm sorry if content creators don't get payed, but then again, I'm not. Make me pay for it. I will or I won't. Don't say your not happy because I'm using a piece of software which is free to use, and has very realizable end-user benefits.