a lot of players do though, you can build a budget deck for any format, but that isn't going to do much at any level but casual, even at fnm most of the people are probably playing tier 1 decks, in which you will very rarely actually get to win anything at your FNM, let alone ever go to a GP or SCG opens because you know the performance won't be good so why bother would be attitude of the player.

the problem is humans are competitive by nature, and it doesn't matter how good you are at the game, the chances of even winning a normal fnm with a budget deck is rare, quite frankly if you win with one of these $30 budget decks than your opponents have to be playing bad or you got extremely lucky. put any of these decks against abzan or twin and they will probably lose 90% of the time.

a lot of people also know this, when i first started MTG about actually 4 months ago, i knew this very well from my previous TCG experience, i started with a budget UW heroic list which rarely won mostly going 1-4 or 2-3 every week, part of it was my play because of being new but the other part was a budget version of already of a inconsistent deck just turns out to be really bad. i'm now playing abzan and top 8 a SCG IQ and weekly get into prizes at my FNM, once again this is partially because i learned a lot since i first started but also because of my deck, i know if i was still using a budget UW heroic i would not be consistently winning at fnm and would of never top 8 a IQ either.

budget builds are great for casual play against friends but bringing one to a fnm and than getting destroyed is pretty crushing and makes some players not want to go back. luckily there is a viable mono red deck for under $30 in standard at least.

this is why a lot of people rather just not play the format/game rather than use a budget deck and at least go to a FNM, a lot of these players just see not as an option because they are competitive but might now have the money to be competitive.