Part of the problem is the way science is funded. I am sure you have heard about "publish or perish". There is a lot of competition in science for grants. I have seen obvious cases of freeriding on someone else's hard work and not crediting them for the data for example, and if you are not listed as co-author or at least shown as the person where the data came from, then it is harder to get your next round of funding.
Also I see examples of people being hesitant to publish their data, as data collection is often the hard and lengthy process, and then people are afraid that someone else is going to scoop you on that discovery in your data. This means that people end up being cautious about releasing their data.
Now, I am not defending this behaviour, but I can understand what is happening. Personally I think that science grants should come with requirements for publishing raw data and methods completely openly.
Perhaps, in the case of data-intensive work, grants should be given in pairs: one research team gets paid to collect the data, and another team gets paid to analyze it.
Also I see examples of people being hesitant to publish their data, as data collection is often the hard and lengthy process, and then people are afraid that someone else is going to scoop you on that discovery in your data. This means that people end up being cautious about releasing their data.
Now, I am not defending this behaviour, but I can understand what is happening. Personally I think that science grants should come with requirements for publishing raw data and methods completely openly.