You must be aware that there are already a number of successful attempts to break into rich Bitcoin wallets. How many centralized exchanges have fallen victim to online robbers? A lot. These online robbers have indeed tried harder and got a few steps ahead of these exchanges' security and got their Bitcoins.
I think most of the successfully cracked addresses has been done because of social hacking or trojan, and not pass brute forcing.
Yes, not brute forcing. But regardless, it means lost or robbed Bitcoins. So it does not matter whether it is through brute forcing or through hacks or phishing or a virus. Whatever the means the Bitcoin was taken without consent, the point is that there is a real threat at hand all the time as in always, 24/7.