Different constraints encourage or force different approaches, which gives you different results. You're not going to have a budgeting meeting over a <1K demo. You're not going to contract out to an artist. You're not going to use a large engine. You're not going to make a doom clone. You're not going to hum and haw over what middleware to use. It limits how much over-engineering you can invent. <1K is a pretty extreme constraint... but it's not that far off from what the demoscene does, and they discover some fascinating techniques and tricks in the process.