I've only ever used a gray key seller once (Kingwin) and that was for Cave Story+ because it rarely goes on sale and I did not want to spend $15 for it.
That being said, I can wait for a game to be on sale and for the most part, legitimate storefronts sell them at a cheap enough price to not bother spending on a gray key seller. Plus I like to support the developer in making more games if possible.
On top of that, there are so many legitimate stores holding so many sales, that it's not even cheaper on the gray market... Steam constantly have games on sale, GOG have constant sales, Humble Store have bundles nonstop, Green Man Gaming keeps spamming my e-mail, although I will never buy anything from them... Not to mention EA and Ubisoft's storefronts... I spend like 5 euro a month on games and i have like 50... All legitimate... Sales and bundles. Nobody needs the gray market. People are just inpatient and want the said game NOW...
Exactly. If you use a utility called isthereanydeal.com, it does all the work for you by searching for the cheapest legitimate option and there are a ton of them. It even gives you a history on how often a game goes on sale.
I'm fine with grey market key sellers if they were well-regulated and had free fraud protection services or had the proposed demands that G2A failed to meet. Nothing wrong with selling spare keys just like selling used physical games but I would love of what I am buying is not stolen. Thieves do not earn their money legitimately.
I definitely will agree there is some impatience. Unless you are Rockstar that stills sells GTA5 for $60 USD, it takes 6 months for a game to get its price cut.
To add a personal opinion that may not resonate with everyone, there are so many games out there and new games coming out every day that it is inhuman to try to keep up with the latest stuff. I have a huge library of unplayed games and I can entertain myself with those until the new game I want is on a deep sale.