Because, as far as I know, the business is not hugely profitable and there's not much scope to change that. Yubico makes a product that is high quality, does exactly what it says on the tin, does not come with any integrated ads/AI or anything else like that, but in the grand scheme of things is fairly niche (I wonder how many people outside of the tech and perhaps gov sectors would even recognise the company name).

There's simply no way they can line up the "here's how we get to 1B users and then mine all their personal data" business plan that some other tech companies can do.