And yet today, I consider the provenance of a product to be more or less my No. 1 consideration in whether I will use it or not.
We live in a world where brands and products are established, then monetized and eventually their userbase becomes just a trading chip that passes from hand to hand. We're giving access or money or trusting systems and we really have no control over the transfer of that trust, data or money.
So unfortunately now, yes it really matters a lot. You're asking me to add code to a website of mine: I want your address, your email, your phone number...I need to know who you really are.
Many people indeed do not care, and just use any cool service they encounter (and yours is cool, don't get me wrong).
An increasing body of people (including me) is more wary of just using any stuff that is out there on Wild West internet. And for good reasons.
In your comment you provide information that would be very valuable to have on your site.
E.g. 'I am a passionate developer and intend to provide Premium services eventually. The basic services you find here will continue to be free.'
(On the browser side, I am aware that various browsers have speech controls hooked up, most commonly inside a Reader Mode—to say nothing of screen readers, which have a different target market. There’s also the Web Speech API which could be used to replicate WebsiteVoice’s functionality using whatever voices are offered by the user’s device. Its quality will be heavily platform-dependent.)