Riot avoids giving them changes because they don't want duplicate work or work that will soon be replaced. This is the nature of business, school, everything. You don't want to take a 1hr walk all the way to the mall if your friend is coming to take you there in 10 min. Life is about avoiding redundancy and saving time and effort.
This is why champs aren't changed or given skins if they have an eminent rework. A lot goes into changing a champion other than plugging in a new number. They have to alter programming, they have to make sure that altering the programming didn't break animations, or break other champions, or break any other programming code. They have to double check that no butterfly effects have happened down the line to code that was based on that one line they changed. Then they have to test the changes, internally and on the PBE. All of this takes a lot of time, effort, and money (people make this all happen), so even minor kit work is fairly extensive. This is why they don't bother with it if there's a rework coming, because all that work and effort will have gone to utter waste when it gets promptly overhauled.
Akali and Eve are actually great examples of this. Meddler had stated that both girls were HIGH on the VGU list, and that neither would get work done in the assassin update. After they announced Galio's rework, Akali suddenly became a candidate for the Assassin class pass, meaning that somewhere in the Champ Update timeline, a rework for Akali got either rejected or pushed back. That's when she popped up on the rework list for the roster update - but you'll notice that Evelynn is very conspicuously missing. This means Eve is still in line for a massive VGU, and is probably why Akali was dropped (to diversify the VGUs, so you don't get a ton of the same thing at once).
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