What's the point of scordatura?

I don't see the point of scordatura at all, I just don't. I've seen pieces with scordatura and most performers play the notes at standard tuning anyway(example, the C minor Cello Suite by Bach is written in scordatura, but most cellists use the standard C, G, D, A tuning for it). So like, what's the point of writing scordatura if it's likely to just be played in standard tuning anyway? To continue with the C minor Cello Suite example, the A string is tuned down to G in the Bach manuscript. This means that Bb written is Ab sounding, the same kind of transposition you get by using a Bb instrument. This means more thinking on part of the cellist, as usually everything is written in concert pitch unless it is harmonics. And you can get that same Ab in standard tuning on the D string, so like, what's the point. If you're going to transpose 1 string, you might as well transpose the whole thing(which is exactly what I did when arranging Hungarian Dance no. 5 for string quartet, transposing every note).

The only case in which I could maybe see the point of scordatura is in the case that the lowest string is tuned down to reach a note that you can't reach with standard tuning. Like getting a low F# out of the violin for example. But even then, if I ran into that, I would just have a different instrument play that F# and not bother with scordatura at all.

Scordatura can be required for several reasons:

To make digitation easier in a piece

To achieve a different sonority: chords that can't be done with normal tuning (or arpeggios, unisons, octaves, etc), a bigger tesitura, microtones...

It's seen in the guitar, too.

4 hours ago, Luis Hernández said:

It's seen in the guitar, too.

But guitar players don't have to transpose if they're playing in say, drop D tuning.  They usually just have tablature giving all the exact instructions that they need (which is never done as far as I know on any of the bowed string instruments).  It seems confusing as hell for only one string in a scordatura-tuned string part to be treated like a transposing instrument, while the other strings are not.  And I think I've seen someone submit a cello piece here on this website that had the bottom string of the cello tuned to B and everything was written at concert pitch without any transposition ... ???

2 hours ago, PeterthePapercomPoser said:

It seems confusing as hell for only one string in a scordatura-tuned string part to be treated like a transposing instrument, while the other strings are not.  And I think I've seen someone submit a cello piece here on this website that had the bottom string of the cello tuned to B and everything was written at concert pitch without any transposition ... ???

I've seen people do both, for example Ysaye does the transposed string notation in his Poeme Elegiaque, but I have also seen the non-transposed notation in works by Vecsey and Saint-Saens. I'm not sure there is a rule saying you have to do one or the other, since the results seem historically inconsistent.

Ysaye: 

Vecsey: