The delay is not that much, with the matches I have watched are not more than 10 second delay.
It depends on the person I guess. if you are watching the match on a multishared IPTV server, the delay could be anywhere from 40 seconds to over a minute if the provider is a very bad one. Compared to that, 10 seconds is nothing. But if you have a regular TV channel that is several seconds faster than the bet365 stream, and many are, a 10 seconds delay is huge.
One thing that came to my mind was to try and use the opportunity to manipulate live betting, but the dalay did not allow such manipulation to be possible. The delay is simply because of the people that bet not to manipulate the matches staked.
That will never work. Sportsbooks have foreseen such possibilities. There is a delay with the acceptance of livebets of 6-8 seconds. That's because the system is checking if anything happened in the match that affects the markets and odds. If something is detected, your bet will get rejected.