Is obliged to (for) widely used? Or it regards only a formal sphere?

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• I’d use TO. I don’t think I’ve seen FOR being used.
- You’re not obliged to answer these questions.
- They are legally obliged to take certain precautions.

• Being grateful
- I'm much obliged to you (often shortened to)
—> much obliged (feel thankful, indebted)

• But it doesn’t require a preposition at the end of a sentence if the topic has been mentioned earlier
Eg “no, you’re not obliged” instead of “no, you’re not obliged to”

Probably more a formal thing, but not uncommon to be found in normal conversations too. Well, I also use it.

Hope that makes sense.