1. Many of those colleagues are too overbooked to spend much time with you.
2. Software estimation is an elusive art, here and probably everywhere. This can easily lead to working a lot of overtime, in order to meet an unrealistic schedule.
3. The company does not, in its heart, believe that there is significant value in writing down documentation on how either the chip, or the software drivers are designed. Much of the chip interface, rather than being in a datasheet-style documentation, is implicitly documented in the driver (and in bug reports). The driver was written by software engineers who have a close email and personal links with the hardware engineers who wrote various parts of the chip. Everyone else has to suffer along with second-level information.
4. Plans and projects change quickly, and often result in, "can you please get this done in a few weeks? You can, right? Great-thanks-good-luck". :)
5. Despite some recent improvements, the next chip decisions are still too strongly influenced by the engineers who happen to be implementing it in hardware.