It has to mainly do with the time savings and disk space savings, as both of these are lesser with incremental backup.

We can't imagine taking a daily full hot backup for a database of size say 500G or 1TB etc...Depending on the hardware configuration, it can take good amount of time and more importantly has an impact on end-user performance and hardware resource consumption. What is the use of taking the backup of whole database, if it has not changed completely ?