Why at night?

Several reasons. Night is typically quieter, and you can only gain access to some places at night. Fewer living persons keeps the energy clutter to a minimum. Darkness is required to get video of certain apparitions and energies. Also some believe that the spirits are just more active at night, probably for the reason that fewer living people are around.
That said I have seen some good evidence gathered during daylight.
 
Utah gave a great answer! The only thing I would add is that most of these investigators like to try and recreate the conditions around the reported experiences. If someone notices strange activity in their home it's most likely to be at night since they are at work or doing other activities outside the house during the day. There may very well be activity, even more activity, during the day but nobody is home to witness it. Likewise, a location like a store or restaurant would have a lot of people and customers moving around and interacting with the environment during the day so any strange activity during this time would get lost in all the normal activity of the business. Which again makes it seem like this activity only happens at night so that's the best time to investigate.

Personally, my most compelling experiences have been in broad daylight so I'm not really sure if time of day is as important of a factor, or a factor at all.
 
Because it makes for better television.
exactly, same with the bigfoot investigations on TV, no known great ape is nocturnal, yet that is when they always think they are gonna see bigfoot, nevermind most "sightings" are actually reported in daylight hours.....lol... even the holy grail of footage for bigfoot enthusiast, the P&G footage, was during daylight hours... but for some reason everyone has become to believe it is a nocturnal creature. mans fear of the dark creates the perfect atmosphere for good TV and is used wisely...
 
When you've been on a hundred investigations, it will make more sense and the "good TV" argument just falls to cynicism.
80% of the residentials I have conducted have been during daylight.
Many commercial venues only allow paranormal teams in at night. It's just not feasible, or even enjoyable, with the general public around.
I see a lot of daylight investigation on TV but people predominantly only remember the dark stuff. Maybe that's what makes the biggest impression.
I feel energies and portals in daylight but the general public is distracting.
And I do admit that it's more enjoyable and interesting at night. My spidey sense is sharpest then.
 
When you've been on a hundred investigations, it will make more sense and the "good TV" argument just falls to cynicism.
80% of the residentials I have conducted have been during daylight.
Many commercial venues only allow paranormal teams in at night. It's just not feasible, or even enjoyable, with the general public around.
I see a lot of daylight investigation on TV but people predominantly only remember the dark stuff. Maybe that's what makes the biggest impression.
I feel energies and portals in daylight but the general public is distracting.
And I do admit that it's more enjoyable and interesting at night. My spidey sense is sharpest then.
That make sense! I dont fear the dark im just scared of whats in it lol.