Why?

Why should a Power Ranger fan who doesn't have any interest in Sentai have to acknowledge it?
It's almost never brought up when a Sentai fan doesn't acknowledge PR. It's an unfair double standard.

Because the majority of what happens in Power Rangers is based off of what happens in Super Sentai, you have to be really ignorant to ignore the existence of something that pretty much controls what's going to be coming in Power Rangers. It's also usual that some sort of respect or acknowledgement is given to original incarnations of everything, which is surprisingly lacking in some PR fandom.

I don't mind people watching just PR or just SS, its when people do things like whine about the Figuart Tigerranger not having a female body or Kibaranger not having a "Tommy" head accessory or when fanart was posted on the PR Facebook page of Tyrannoranger, AbareRed and Kyoryured and people were accusing the artist of putting in a "Fanmade character" or the people saying that Gokaiger was stupid for not having more Zyuranger (or "MMPR") over anything else is when it bothers me.

doggie c is same in spd/dekaranger

Sentai isn't the original, it's just where the footage came from.

Power Rangers isn't an adaptation, a remake or a sequel, it's its own show. Even when lifting stories, it still isn't Super Sentai because it's born from an entirely different culture and set of rules.

The same fight footage is where the connections end.

That's completely not true. Like, at all. I guess Zyuranger and MMPR both didn't have a Dinosaur theme to the suits? Dekaranger and SPD weren't both about police? Magiranger and Mystic Force didn't both involve wizardry? GoGoV and Lightspeed Rescue weren't both about rescue forces?

Come on. Yes, they are separate entities but there are countless connections in even the most different of series. They are still adaptations of a Japanese show to a Western Culture.

That's an unfair assessment. The fight scenes are what's lifted. While some plots are taken from the Sentai counterpart, just as often we're given completely original story lines.

And look at the differences.
Dekaranger and SPD take their police angle in two completely separate directions. Magiranger and Mystic Force have two completely different magic systems. And EVERY series, both PR and SS, are about rescue forces.

Also, you can't use similar themes as a counter point, or else Zyuranger, Dino Thunder, and Kyoryuger is the same series 3 times over, because dino themed suits and whatnot.

And Megaranger was turned from a video game into a space Opera. Whatever Lost Galaxy was taken from...well it's clear from the awkward editing that it wasn't a space show. Go-Onger is certainly no RPM. There ain't no angels in Megaforce, it goes on and on and works both ways brotha.

But you specifically said "That's where the connections end" which is completely factually untrue.

Because it is, the only connections you drew are from limitations of the footage they took. And to be fair, actually, often Power Rangers has managed to go beyond those limitations, considering more of Power Rangers is original stories than it is Sentai lifts. The more you made me think about it, the less I saw similarities and I barely saw any at the start.