Well, if that 'realisation' happens to SQL Server DBAs there will be more optimisation work than ever for the SQL Server consultants.

Rebuilding indexes in SQL Server is not a waste of time. SQL Server != Oracle. Very different index architectures. Very different 'best' practices.

Sure, the fragmentation itself may not be an issue ('may not be', not 'is not'), but the low page density that results from page splits or lots of deletes can be very nasty. Nothing like a table with 20000 rows taking up over 5000 pages when it could fit in less than 2000. Hell, I've seen a table with about 2000 rows take up just under 2000 pages because of the pattern of deletes and because the indexes were never rebuilt. That's a waste of space (in memory, on disk, in backups) and of time (backing up, reading off disk, consistency checks, etc)