We can't boot homebrew on a console because manufacturer doesn't want us to do so.
Then, in that case, people look for breaches. Then they publish it. Then manufacturer fixes them.
Often with a firmware update.
These recent & secure firmware updates come pre-installed in recently purchased consoles.
So there are two kind of people.
1) people who like online stuff and keep firmware up to date.
for these people, after a few updates, homebrew is over. definitely. it's their choice.
2) people who like homebrew better than online stuff and added features in newer firmwares.
they have to keep their old firmware safe. with some soldering skills they may swap between firmwares versions, eventually, with heavy mods (on 360).
tmbinc found, relatively quickly, maybe one year after 360 launch the breach in 4532 & 4548.
chronology was a bit odd, but 1st a hooded guy made a demo in germany, then a few months later an update fixed the breach and the details of the breach appeared publicly. many already updated and breach was gone for them, but they could downgrade later with a smart electronic device (thanks to a nice cooperation between the people at xbh site), one year later.
those who felt the hooded guy was doing good didn't update and got no problem to get advantage of the breach in order to boot linux, thanks, once again, to tmbinc's low level published drivers sources. tmbinc was not alone I think, but I only remember his pseudo at this time. See tmbinc blog for details (debugmo.de)
So, the conclusion is, with security technology improving over time, in the life cycle of a console, there is almost always a mistake done somewhere in the initial design, and the security breach needed for homebrew appears, but is a short time window, quite narrow sometimes, when you must give up updating the console firmware. if you miss it, it's over. better wait for next console generation if that happens or buy quickly another console from the shelves that is still with older firmware.
Nowadays you have to choose : homebrew or online. people with money who want both, will purchase two consoles, one for online and up to date features, and one for homebrew.
If you want the details about why security works well now, read articles about security chains. chain starts inside the cpu itself (it's too hard to explore it physically to read unique -per console- secret keys inside etc...). keys are used at each iteration of the chain to verify authenticity of next element with 2048 bits cyphering (no way to crack in human lifetime), and thus, security engineers are beginning to know their stuff now. To find breaches is harder over time. I think breaches happen only at launch time when engineers are pressured to release their work on time, but after that they have the time to close all breaches with firmware updates.
so the recipe to get homebrew is :
- buy a launch console
- never update it
- wait (need patience)
For 360, right now, if you purchase the console, it's too late for homebrew, it's too well secured.