Why RewriteRule index.php [L] is no more sufficient

[eluser]InsiteFX[/eluser]

Code:

# PHP5
<IfModule mod_php5.c>
    RewriteRule ^(.*)$ index.php/$1 [L,QSA]
</IfModule>

#PHP4
<IfModule !mod_php5.c>
    RewriteRule ^(.*)$ index.php?/$1 [L,QSA]
</IfModule>

But the ? is required on some hosting providers!

InsiteFX