Re: "text and data mining"...
I've been in your position, and I do wish that companies would be more accepting when people offer to help improve their services. I would also wish to weaken copyright protection for some types of compilations. For example, when Oracle and Google were arguing over the copyright to function definitions in an API (rather than their implementations), I was firmly on the Google (they should not be copyrightable) side of that argument. It sounds like I would want what you copied to be freely available as well, but that would be a blanket policy, not one triggered by their action or inaction, and if my assumption is incorrect about what the data entails, if the publicly-available sets contained more original work for instance, I would have the opposite opinion. The challenge is that I cannot bring myself to accept that their decision not to is severe enough to cancel copyright over it. I derive this unwillingness from two mostly independent reasons.
The first one is that, there are a lot of complications whenever an external person offers to help with things. I find your descriptions believable and I stand corrected that you had no commercial motives, but I've had experience with the alternative. I work in security, which means that my employers are frequently open to submission of security problem reports from the public, and I have reviewed these. They occasionally turn up useful things, which is why we do them and offer to pay people, but I've also had to deal with many people who offer things that are not security problems either because they are attempting to get a payout or because they don't understand how systems work well enough to know what we could fix and what things have a security-related outcome. This means that I've frequently had to decline submissions. And no, I'm not the guy who declines real security issues because I don't want to fix them; those companies don't have bug bounty emails in the first place. I have submitted problems to those people before, though. Using anything where declining an offer of help is sufficient evidence would require a lot of work to filter out unreasonable submissions, and I am not comfortable assuming that would happen.
The second is that I generally oppose restrictions on copyright which are about an action. Something should be covered or not based on simple rules, rather than attempting to control what the creator does with it at all times. Many such regulations have been suggested, usually by people who would really prefer that copyright would be eliminated but they don't find many to agree with them. If you don't update your website, that doesn't make your work less valuable. It's quite possible that if you did update it, your work would be more valuable, but copyright protects work because of its original value, not to mandate the creation of any available additional value later. I may be annoyed by people squatting on things they have, but I don't think that qualifies me to punish those who do; it certainly doesn't for people who do that with physical or financial things, so I don't see why it should if those happen to be copyrighted works.