why do I have three copies of data/log files per database on same server instance
It is possible that your databases were set up this way. To find out you can run this query:

SELECT DATABASE_NAME(database_id) DbName,* FROM sys.master_files ORDER BY 1;


It lists all files that belong to each of your databases.

If the databases in question list only one file each, then something outside of SQL Server is creating these copies. 

Otherwise each database is just split into multiple files and actually taking up that space. In that case you can really only either delete databases or increase the disk size.

It can have performance benefits to split a database into multiple data files. However, splitting the log into multiple files is usually unnecessary as SQL Server is writing always only to one of them at a time.