Because it provides a technical update of the progress they are...

Because it provides a technical update of the progress they are making. Whether the progress is that they've hit a brick wall and the technology just does not work at all, made very little progress sitting around doing nothing, have been slowly chipping away knocking back one issue after the other and making progress overall, or have finally completed and fully tested the working prototype that will change the world. Whatever the update is, affects what a reasonable person might perceive the share price to be worth - whether that be lower, the same, or higher. Almost every market announcement will likely be price sensitive for this reason, other than appointment of a new company secretary, or reporting minor changes to holdings.