And why do I have to tell them the current time, seems to me that's extra info they can figure out on their own.
You don't have to report the current time, just the time you crossed the fix, which may not be the same. It may take a minute or two to write down the time you crossed the fix, compute your estimate to the next fix (not everyone has GPS), and determine the name of the next fix as required for the "PTA-TEN" reporting format:
Position
Time
Altitude
Type
Estimate
Next
If you are able to report exactly as you cross, you can omit the crossing time by saying "Center, Cessna 123, Bungo intersection
now", but otherwise, they need the time you actually crossed. And remember that these rules were written when a fix crossing often involved a conversation something like this:
"Navigator to Pilot, approaching Bungo, turn left new heading 045 in five, four, three, two, one, now, left 045."
"Pilot to Navigator, turning left new heading 045."
Navigator logs time of arrival, computes actual leg time, computes actual leg ground speed, recomputes wind, and then computes new estimate to next reporting point using pencil, paper, and E-6B.
"Navigator to Pilot, I have our position report, ready to transmit."
"Pilot to Navigator, the radio is yours."
Navigator: "Center, Army 42756, position report."
Center: "Army 42756, Center, go ahead."
Navigator: "Center, Army 42756, passed Bungo at 36, seven thousand feet, IFR, estimating Gonzo at 55, Pooky next."
"Navigator to Pilot, transmission complete."
As you can see, the position report might actually be transmitted several minutes later than the crossing time. However, ATC needs the actual crossing time in order to ensure proper separation.