Why does attempted murder carry a lesser sentence?

Maybe if you're stealing a Tesla. Macs are pretty expensive so you might get punished harsher for that than for stealing a Soviet-era Lada.

I have just attempted to murder you by carving your post number into a bar of soap, jacking off on it to activate the sympathetic magic, and then stabbing the bar of soap with a kitchen knife.
I did this with the full intention that it would cause your death. I believed ir would cause your death.
What will my punishment be if you survive?

This line of thinking is not in line with English law tradition and is not liberal (in the classical sense). Your line of thinking leads men to try and stop crimes before they happen. This is the foundation of communist legal systems. You should move to China.

Everyone in society is a danger to society. Cry me a liver.

When a murder is not successful the situation is usually different too on average and there is a better chance that the person will actually be "corrected" in the so called "correctional facilities" so it's less sensible to lock them up that long.
All that aside, most countries' "correctional facilities" fail to actually correct anything, especially in America they are self-perpetuating and a drain to society (but that doesn't matter as long as a few special interest groups make money, what a nice dystopia).
Germany has issues too, by the way, first among them is "Beugehaft", substitutional incarceration for not being able to pay something.
Many people end up in jail when their only "crime" was longer-term insolvency over sometimes simply a parking ticket or some other shit.

bro this isn't talking about sending someone to prisoner for decades for selling weed or giving someone a life sentence for not paying an air conditioner repair bill (which has literally happened in the U.S.)
we are talking about someone who is willing to murder, that is quite a bit different.

everybody is willing to murder when pushed far enough. The question is have they murdered anybody yet?
the attempted murderer hasn’t killed anybody, nobody is dead. If society scares you, you could always hide in a big cardboard box with some pillows.

The joke is that the previous owner of the store is called Chuck so if you replace "Sneed" with "Chuck" you get "Chuck's Feed & Seed".

How are you going to take a corpse to court?

You don't realize you are on a slippery slope. Legal systems aren't perfect. Punishing only the act preserves human liberty from forces that would be too zealous in trying to create utopias on Earth.

>everybody is willing to murder when pushed far enough.
no they are not , homicide is a supremely unnatural act. This is actually backed up by research from the military that showed that only like a fourth of soldiers in combat were willing to actually kill.

offer a summary execution and if he doesn’t object, he is put to death by being thrown off a skyscraper into rush hour traffic with a crate of TNT strapped to him