Everyone tries to compress a workout into a single time interval in the day, where you do n sets of each exercise and then go home. To do three sets in three minutes, you're going to have to pick a very conservative goal. Doing 5 sets spread out over the entire day, I could lift more and saw results pretty much right away, and really for the first time. I'd exercise while waiting for things like the drier to ding or toast to pop up, a file to download, a commercial break or a cut scene to finish. But, I had to have exercises I could do at home, which takes some creativity (or a lot of money).
Your body is conserving resources. The whole point of 'exercise' is to trick your body into thinking that you are an active person who needs to spend the extra resources to build and maintain large muscles, cardiac or lung capacity, or all three. If you are actually active you don't have to 'work out'. Your life is work, and your body adapts.
Once I got past that initial roadblock, I got results even from the gym, but I was able to be more consistent doing it at home.
The trouble with putting on a lot of bulk though, is if you stop. Exercise burns a lot of calories. Persistent exercise therefore changes your notion of what a 'normal' amount of food is. If you stop, it probably due to some major life event, and adjusting your notion of 'normal eating' might get lost in the mix. Which is probably why a lot of pro athletes chunk up when they retire (or get retired). Going from 3-4000 calories a day to under 2500 is quite a lifestyle change.