Everything depends on your expectations. Trajectory is either calculater or observed, but observation is always required. Ballistics programs are available (some free), or calculate yourself. For rifles, zero @25, is on the paper at no more than +3 @100, and if your target no more than 100 yards, & that meets your expectations, then go no further.
If not, then know your trajectories. If target shooting, exactness is important. If hunting, Point Blank Range (PBR) is important. PBR is decided by you, and is calculated based on the kill zone for your quarry. Example: kill zone for a moose might be 16 in. dia., but for a white tale deer it might be 8.
PBR has little relevance if 100 yds is tops, but if you might shoot at 150, 175, 200, ..., then its no longer just "nice to know". Ballistics programs reveal ball-park details, and range time refines it for your specific rifle & ammo.
In my case, I make trajectory printouts for each, and use them to know my capabilities. Follow-on range time gives confirmations, or reveals changes that must be understood & applied.
I enjoy my 7mmRM, .45-70, & 5.45x39. With a 4" PBR, my 5.45x39 has a max PBR of 248yds., dead-on @212, 6.5 low @300, -.25 @25yds, & +2 @100. If I shoot @300, then I'd better hold-over 2.5 in., or I miss the kill zone or lose the match. For my 7mmRM max PBR is 236, dead-on @202, -8 @300, 0 @25, & +2 @100. For my .45-70 max PBR is 131, dead-on @112, +.6 @25, +2 @75, +1 @100, & -11 @175. Note: All numbers change if I choose a different kill zone.
All of the above comply with zero @25, and no more than +3 @100, but there's a lot going on in between and after 100 that's critical to either target shooting or hunting.