IE8 developed a lot of problems despite being the last browser to run on Windows XP.
I wonder if it got neglected because Microsoft was not interested in XP especially after extending its life so long.
Anyway both IE9 and IE10 were big steps forward. On Vista + versions of Windows they use a more secure environment that became available on these operating systems. Running IE8 on a newer system definitely leaves unnecessary potential for attack.
BTW Firefox didn't use that environment even on Vista and 7 but I don't know if that is still the case. Chrome always used it.