You just haven't run into a good Lux support. I build tank Lux that isn't afraid to get in there and Shield and return fire. By the time we are out of laning phase my adc and I have taken over the game and they have 2 damage items with like 3 to 4 kills and over 120 CS, First Blood Tower to boot. I think a lot of adcs and supports dont really understand how to play the different match ups and what to expect and what is okay and what isnt okay. The following is sort of the rules that I personally have found to be successful.
My rules as support: I am the early game carry. You focus on farming and poking, not deciding when to all in. You are my b*&ch until we out this lane. If you get out of position it is not my job to save you if I think it will make us both get killed. If I get engaged on you attack whoever the biggest threat at the time;IE Soraka over Vayne but Vayne over Thresh modified by current life totals etc, If you are playing ADC then you should know this calculation if not Just attack who Im attacking. If I ping you better listen to it.
My rules as ADC: You better not take my CS, You better not let CS waste/die to turret or enemy minions, You better know how to harass enemies safely. You need to understand MY RANGE AND POSITIONING and NOT go all in when there is no possible way I can get there. If I get engaged on you must Weave as many autos as you can while you are casting your spells! DONT YOU DARE RUN AWAY like a little chode when you could have dealt 500 -/+ damage in this fight over the space of 7 - 10 autos. *sigh Yes it triggers me that in 2017 this is not a standard practice among all Support mains...., FINALLY After we leave this lane you find the carry and follow them. IF I'm not carrying then go help the team while I solo farm EXP and come back with a vengeance....
LOL TLDR I Know but any of those support mages can follow this to the TEE and I'm fine with that...