One thing to take into consideration is FTL is a very dangerous manoeuvre. In the miniseries they seem shocked that it would be even considered as an option. Not to mention that even with FTL the colonial systems can only go so far, and it uses a ton of fuel. The fleet is constantly having to hunt for supplies, losing ships, and having problems due to their means of transport.
Now imagine if there wasn't a fleet of deadly cylons following them and instead there was a fleet of deadly cylon bogeymen "out there". You might not be too inclined to explore too much.
tl;dr the type of travel we see in BSG is uncommon and dangerous pre-cylon invasion, they had fairly strong reasons to stay in "known space".
The script leading up to their first jump:
Adama: Bring me our position.
Specialist: Yes, sir.
Tigh: You don't want to do this.
Adama: I know I don't.
Tigh: Because any sane man wouldn't. It's been, what, twenty,
Adama: We trained for this.
Tigh: Training is one thing, but - if we're off in our calculations by
even a few degrees, we could end up in the middle of the sun.
Adama: No choice. Colonel Tigh, please plot a hyperlight jump from our
position to the orbit of Ragnar.
Tigh: Yes, sir.
They indicated that they had not done this in twenty-two years, and this is within known colonial space. It is pretty safe to assume they don't go jumping around willy nilly for the sake of exploration.
And as far as non-FTL travel. I again point you to the dangers of the cylons who are out there somewhere.