There can be many reasons for delay.
The crew not even buried yet - one.
Polish Presidential elections - two. Where the party of late President is about to put forward from them Kachinsky's own twin brother.
Waiting for the interest to die out, public attention re-switching onto something new - and then release the materials - three.
Hard to say.
But surely absence of even minimum data only feeds rumours and at present helps to build up tensions.