Defrag Index

I just got turned onto Idera's DBA tools, and was trying them out, finding out that a lot of tables are 80-90% fragmented.

These are tables that don't have indexes... Am I misunderstanding indexes if I wonder how an unindexed table gets fragmented?

Why if I run a command as follows...

dbcc indexdefrag(Northwind,any_table)

...shouldn't that defrag the any_table table? When I do that, it just comes back and says it is still fragmented.

Another thing I don't understand, is that I had index drops and rebuilds scheduled daily when no one is around... How are some of these tables all fragmented?

Thanks--