If they cannot raise rest of the funds, then wouldn't it make sense if the funds raised so far be returned (similar to crowdfunding where the money is returned to donors when the target cannot be reached). If the company needs $3m for an acquisition, and raised only $1m, it doesn't make sense to keep it, they have to spend on a less optimal project elsewhere different to the reason they need the funds in the first place (guess this would be a different for a fund though).
Especially in the case if they cannot raise the funds because the share price < issue price, then its almost like a scam to keep the money, wouldn't it be a duty to "act in shareholders'" interest to return the money to instantly unlock shareholder value?? Its kinda like oh hey I need to raise $100 to buy a shovel to dig for gold, give me $10 for 10% share and we'll all get rich after. Later, oh I'm sorry I cannot find enough investors but I'm gonna keep your gold anyway, I'll think of something to do with it!