Oracle Default User problems?

After oracle is installed, there will be many default users. How can this problem be solved?
Anonymous, ctxsys, Dbsnmp, HR, MDSYS, ODM, middleware, Oe, olaosys, ordplugins, ordsys, outln, PM, pblic, QS, qs_adm, qs_cb, qs_es, qs_ OS, qs_ws, RMAN, Scott, sh, sys, system, wkproxy, wksys, wmsys, XDB

Both sys and system users cannot be deleted. Others, such as rman, are also useful. Others are used to test the database sample.

Key Role of user passwords
System Manager yes: the System user created for the DBA
Sys change_on_install Yes sys users who have data dictionary tables and views
Scott tiger no detection mode, Oracle Reference Mode
Internal Oracle Yes sys is not a real user
Demo demo no detection mode, Oracle Reference Mode
Dbsnmp No Enterprise Manager Administrator you
Outln Yes stores row output
Missys no is used by Oracle service
Aurora... N/A Yes Database Registration
Ordplugins no internal media for Oracle
Ctxsys no internal media for Oracle
Ordsys no internal media for Oracle
MDSYS no internal media for Oracle