When I am running the following search:
index=main sourcetype="access_combined_wcookie"| stats list(useragent) as Browsers | dedup Browsers consecutive=true
The dedup command is not removing duplicate entries in the browser field.
Can someone explain to me why it is happening?
Did you try mvdedup?
index=main sourcetype="access_combined_wcookie"
| stats list(useragent) as Browsers
| eval Browsers=mvdedup(Browsers)
While using dedup on a table, splunk will deduplicate values (read cells) of a given field. Your result has a single value/cell (regardless of having multiple values inside it) so there is nothing to dedup.
What you're probably looking for is something like:
index=main sourcetype="access_combined_wcookie"| stats values(useragent) as Browsers
OR
index=main sourcetype="access_combined_wcookie"| stats count by useragent