Outside of early crafting, is there anyr eason to spend materials on white-blue items ?
White items not so much.
For Magic Items with one desired high affix (t4 or T5) or maybe two desired affixes you cna definitely try using a Rune of Discovery and then reroll the added affixes with glyphs of chaos.
This strategy does work very well on certain item types, that don’t have a lot of affixes on certain slots. (For Example boots only have 7 Prefixes in total with some of them being rarer than others. So if you already have one desired stat (like Str or Int on them, rerolling the second prefix that was added by the Rune of Discovery into Movement Speed is very easy).
For suffixes on slots where you only want to have resistances, this also works very well, because early on in your progression most of the time you don’t need very specific resistances and you can be more flexible.
This strategy does work a lot worse on items slots with a lot of affixes, like Body Armour, Helmet or Relics (because there are tons of class specific affixes)
if it high rolls several rare affixes, like +skill level for instance, it would be better to get a blue in most cases as you can then add affixes to the other slots you want