@RIOT Why are some Summoner Icon only available on some server and not others?

I'm on EUW server and I really like to play Nautilus most of the time I go top lane or support role, and just recently I found that this icon exists:

http://3.bp.blogspot.com/-PmxsvAkiIBo/VqFlJT4ymUI/AAAAAAAA3LY/JGPPCdU2u4Q/s1600/profileIcon1103.png

A wonderful icon just for showing my likeliness in playing Nautilus, a fun champion (it's his anchor by the way if you're not familiar with his model). Sadly, this icon is only available on the OCE server, so I'll have to pay the transferring of my account 2 times, for going to OCE and then back to EUW (5200 RP) and then buying the icon (250 RP).

The Fizz icon:

http://1.bp.blogspot.com/-AchT4PG_9qs/VMVVfceXFcI/AAAAAAAAiSs/YdXkW1W8y6A/s1600/profileIcon773.png

was released for a short time on the other server (basically, the Nautilus icon and the Fizz Icon were part of an event called "Ocean week 2016") but why? Why that icon and not all Ocean week icon? But most importantly, why were the icon then removed? You did this with champion splash-arts, (make them globally the same,) why not with the shop too? Is this just overlooking an issue for some (like me who want this icon without spending a whopping 5200 RP just for transferring reason) or is there some motivation?

Just to say, the Harrowing and Bilgewater Icon feels special, you were there during that event, you did your "quests" and you got your reward, feels amazing showing it because it means you were there, a long time ago. But then you see someone with the icon I want, a dumbass who spent 5200 RP to get an Icon, FeelsPrettyBadMan, I'm just asking for an icon available on another server, not for legacy skin or "legacy" summoner icon (Harrowing, Team builder, Bilgewater) anyway...