The issue with tabs as indent level is that there are two reasons to indent. The first is for logical scoping, where tabs do indeed make sense. An example would be

    int main(void){
        indentedStatement()
    }

However, the second is for aligning multi-line statements. Something like:

    int main(void){
        foo(bar,
            baz,
            54
        );
    }

Here, the indenting on arguments baz and 54 really should be aligned with the argument bar. If we really want to combine both use-cases that involves a mix of tabs and spaces. Tabs fist for getting the number of nested scopes, with optionally spaces to align text.

Meanwhile, mixing tabs and spaces is almost universally seen as bad. This makes sense because it is not visible where the tabs end and spaces start. This can easily lead to inconsistencies that are invisible to a writer, but are horrible for a reader with a different tab representation.

If you believe that indenting like this is a bad coding style, how do you suggest those statements should be formatted?