Well, I think many of the points in favor of a homebrew have already been made. And I have faced the exact same problems in generating interest in a homebrew setting compared to running a established setting--much of the advice here I could use for my own homebrew game.
One of the biggest things that has held up my homebrew game has been the 3.5 releases & supplemental rule books (waiting on UA and PsiHB now; any OA updates would be nice, too). I really don't like to kick off a game when a new race, core class, or mechanic in a supplementary book is released that I'd like to add to the game (& which may cause a significant shift in the homebrew setting). It's an obsessive trait on my part (and an annoying one at times), but sometimes it does help solidify a concept I have for a game, whether it's a "Crunch" of "Fluff" aspect.
A big advantage to a homebrew is that you can easily incorporate elements from existing settings that you like, and with a little time & work, make it a reasonable part of the setting rather than have it look like some badly-assembled Frankenstein's monster of a setting. It also allows you the freedom to exclude anything you want as well. (Sure, you can do this with an established setting, but you run the risk of having problems/issues with your players over it, especially if it's a well-known/well-loved setting.)
As for why I even expend so much time & energy into a homebrew? Well, to a certain degree, it is an obsession, on my part---it's a way for me to be creative. It's also a way for me to get all of my D&D-like ideas out of my mind & used, rather than just sitting in my brain & mingling in to ideas for my writing (which I'm trying to keep somewhat unique & non-D&Dish).
Also, it's cheaper for me. I don't feel the need to purchase all of the supplements for a setting, especially ones that may be relevant for the PCs (like, for example, the Underdark FR sourcebook for any sort of drow, duergar, or svirneblin PCs).
I can borrow elements from anything & anywhere for my homebrew--and I often do. Whether is a plot hook from a story, a city from a old sourcebook/setting, or even a NPC from a CRPG, I'll use it if it interests me.
I think one of the big reasons why I'm into homebrew settings instead of established ones is due to the information base--especially for settings like Forgotten Realms, Dragonlance, Star Wars, Marvel/DC, Lord of the Rings, etc. Though there are some players who may have knowledge about the game to understand certain nuances & reference, not all of the players may share that level of knowledge.
And to a certain degree, some players emulate elements of an established setting a bit too much, whether it's a prominent NPC (Elminster, Drizzt, Raistlin, etc.), a unique race (draconians, saurials, thri-kreen, etc.), or even unique abilities/concepts (spellfire, Chosen of XX deity, wild magic, etc.). It gets a bit tiresome after a while.
Ultimately, keep on keeping on, if you will. Homebrews really do have potential to capture the imagination of your players--sometimes it just takes the right "spark" to set it off.