Interesting... Ohg jbhyq univat n phefr erobhaq bss lbh ernyyl ubyq hc nf "qrsrngvat" va n pbheg bs Ynj? Fancr'f nanybtl bs n zna gevccvat ba n onol pbzrf gb zvaq. Fgvyy, vg zvtug yrnq gb na vairfgvtngvba vagb gur znggre, juvpu pbhyq fgnyy guvatf.

If I remember right, it's implied that botched Transfiguration is a painful way to go -- it's compared to a severe illness. If its consequences are sufficiently well-known and unpleasant, it could be that it's not attractive as a suicide method.

On the other hand, Transfiguring your brain into aspic or something like that sounds pretty quick and reliable to me. Perhaps that's difficult for technical reasons.