From a player perspective, this would be a great feature -- you'll probably find that from your poll. Yet that gives you no useful information for the game itself, as it's an incredibly biased poll; it's looking at the situation from only the player's perspective.
The unfortunate truth is that games cost money to make and sustain. Developers have to make a profit, or there isn't a next game. It's tough for players to deal with...and it's also tough for designers to deal with. Believe me -- if I build a game, I'd LOVE to give it to everyone for free. That's just not financially viable though -- I'd starve.
So, from a company perspective, this is effectively giving a player who wishes to rotate champions a 50% increase in IP. Now, players who constantly want new champions are a strong source of RP revenue: they'll buy skins and new champions with IP or RP, so long as they've got the newest, shiniest, most fun character. Giving them 50% less incentive to make monetary purchases isn't good for business.
Now, I noticed you say this:
I absolutely agree, but some people don't have the time or money in order to attain such a variety within a reasonable time frame. Although I'm mainly speaking for myself here.
And it's entirely true. But, again, Riot doesn't INTEND for everyone to have a massive variety in a reasonable time frame. You can unlock 1-2 champions in each role pretty quickly, but there is intentionally a harder catch-up period because the company needs to make a profit.
That said, with the new, slower champion release schedule it IS possible to gain more IP than you'll spend on new champions once you have them all -- which means it is possible to catch up. To do it entirely for free, however, takes time...and that's the system working as intended.