Claims experience lacking

This is the third time I have had to claim with Discovery and all 3 times were a nightmare. The first time was a claim for our BMW in June last year. The accident happened on a Saturday night, and thus I was not surprised when they wanted to investigate the claim. The lady who investigated my claim was extremely rude and told me(I am the client) that I am unprofessional. I eventually refused to deal with her and only worked through my broker. The claim was eventually approved and I got my car approx 6 weeks after the incident. In Feb this year, my stepson had an accident where a taxi drove INTO him. Thus was on a weekday, in broad daylight, and also expected a troublesome claims experience based on what had happened in the past. I was surprised when the claims advisor told me a few days after the claim that the car was a write off and requested the appropriate documents. Surprise surprise, yesterday I get a call from another lady, who-jup you guessed it-is investigating our claim. I will always comply with an investigation as I realize the person is just doing their job. This lady has been much more friendly and easier to deal with, so big ups to her. I would like to know from Discovery if every claim I ever make will be delayed due to investigation. Why do you need to visit the site of the accident, what does the cars service history have to do with the fact that a taxi hit our car, why do I need to sign permission forms(what type of information are you looking for and can I maybe help you to get it quicker). Also, why would a not at fault accident that happened in the middle of the day need to be investigated?