Because of how modern disk drives work there was NEVER a way to truly secure delete. A rotating disk will do bad sector replacement, but data can be read from bad sectors with the right tools. SSDs never write to the same place twice, then constantly remap pre-cleaned sectors to the old logical offset, and SSD bad block replacement moves a bad sector out of service, and again can be read with the right software.
A company like Apple, that gets sued because they have money in the bank, cannot afford to have a service or utility that claims it provides a secure delete if it does not 100% provide that service.
If you are concerned about sensitive data, you should be using System Preferences -> Security -> FileVault, so that deleted files are just a bunch of random bits. This will get even better when the new file system in Sierra is more commonly used by Mac users.
If you do not want FileVault, and want a srm tool, then follow the suggestions from sesser and install your own flawed tool, which keep Apple libel free.