Four reasons, and they are distinguishable.
Your role
What you can see is set by your role. Somebody without access to an area does not see that area, rather than seeing it empty.
This is also true of the assistant: asking it for something your role does not cover gets you told which access is missing, not an answer worked around the gap.
If you need access, the person who administers your workspace can grant it.
A connection that is not there
Whole areas depend on a connected system. Operations is thin without a field service system; receivables need accounting software; marketing performance needs the advertising and search accounts connected.
Check Technology for what is connected before concluding a feature is missing.
Something not released yet
Not everything in the platform is available to everyone at once. A feature still being tested is not shown, and the wiki does not document it either — so if you have heard about something and cannot find it or read about it, that is usually why.
No data yet
Some screens are genuinely empty until there is something to show. A first month has no year-over-year comparison; a business with no stock has no inventory figures.
A figure the platform cannot support well enough is also held back rather than shown — see how confident a number is.
Telling them apart quickly
Whole area missing from the menu — role.
Area present, screens empty — connection or no data.
One figure missing from an otherwise full screen — confidence, or something uncategorised behind it.
If none of those fit
Say what you expected to see and where. See getting help.