Firstly, if you're going to raise at all, why not raise when you are in the strongest possible negotiating position (ie when you don't actually need the money)?

Firstly, if you're going to raise at all, why not raise when you are in the strongest possible negotiating position (ie when you don't actually need the money)? Presumably they think they may need the money at some point in the future. If you are burning through your runway that gives you additional pressure and VCs can run out the clock and delay rounds to try to get a better deal. Having cash committed takes all of that off the table, and even if there is a downturn etc you have your funding secured from a position of strength and don't need to go cap in hand down the Sandhill road during tough times. Secondly (some) VCs bring more than just money to the table and by becoming part of their network you get access to their help etc. In my experience even for some pretty big-name VCs this is a dubious benefit but some people like it. Thirdly the founder gets to act like a bigshot raising a pile of cash.