Needle jokes

Why do people keep adding an extra s after 'needles'?

I don’t see the point, it’s needless.

My girlfriend said she was going to get a massive tattoo of a snake on her back.

"Do it," I said. "But it might hurt you."

"I know," she replied. "But it's only a needle."

"No," I said. "I mean being single."

Just got my vaccine, but they stuck the needle in my leg.

I spent the following day thinking “my Pfizer killing me”

I'm so stressed that I'm going to try that Chinese thing with the needles, what's it called?

Oh yeah, heroin