Taking a hot shower does kill some germs on your skin.
But for some germs and bacteria the hot water is not hot enough to kill those germs but if you use antibacterial soap to wash your body with those germs and bacteria are usually killed by that antibacterial soap.
Then the bacteria and germs are washed off your body when you scrub good enough and the germs and bacteria get washed down the drain.
So even if the germs and bacteria are not actually killed by the showering the bacteria and germs that fall off your skin get washed down the drain so they come off of you.
That's why you should take a shower at least once everyday using good antibacterial soap to kill germs and bacteria.
Even if you don't look dirty there can still be germs and bacteria on your body.
I've taken showers when I thought I was clean and I couldn't believe all that dirt that was actually falling off of me and into the shower water.