A long, long time ago, in a data centre far, far away...
Back in the day, a multi-user system might have had a single 4.8M hard disk, shared between the operating system and all its users. It made sense to use tabs instead of lots of spaces for indents, because each tab saved you 8 spaces - a pretty good compression ratio, and a worthwhile saving in disk usage.
Then came a period of chaos, where people started muddling up their desired indent with the size of a tab. Decent editors always let you separate the two, but poor quality editors confused them, and so you ended up with tabs being re-defined as 4 characters, or even sillier things.
Given today's disk capacities, there is really no point in bothering with characters in your source files to achieve indents. Be specific, and have however many spaces you want. A decent text editor will let you configure the Tab key to give you whatever indent you want, but for goodness sake configure it to do it by way of spaces.
Back before the sizes of tabs got confused, I've used editors which would do the following:
First press of Tab - insert 4 spaces.
Second press - remove the 4 spaces and insert a hard TAB
Third press - add 4 spaces.
etc. It was all very clever, but unnecessary now.