I'm an investor and I think it's worth holding onto a currency if I see it as a good store of value, it doesn't matter if not everyone on earth is using it (eg: does everyone use gold? Could everyone use gold? No. Still a good store of value). So please don't speak on my behalf.
There's no such thing as a bitcoin customer. And by growth, the only obstacle is number of transactions/block which is limited by design.
But there's no tps limit that we wouldn't blow through in a day if it were free. Building a distributed DB? Nah, just dump it all in the blockchain and make the world hold it for you. Without a limit, and the prices that come from approaching that limit, the system would never reach a balance.
The goal is that transaction costs pay miners. That only works if blocks are small enough to reasonably process and scarce enough to justify paying for.
For everything else, build a sidechain and do your micropayments on it - link to BTC every now and then for larger fund transfers.
The price has actually been dropping consistently since the 31st of July.
Granted, this hack has caused a the drop to be bigger, but attributing the entire drop to it makes no sense. The timeline doesn't fit.
The most likely reason the price has been dropping is because the Bitcoin miners have ran out of reasons and deadlines to stop the bitcoin hardfork which will cause an increase in block size, which is the main reason why Bitcoin is artificially blocked from accepting more customers and grow.
Investors likely don't think its worth holding onto a currency if it has (and reached) an artificial ceiling.