The man who invented it doesn't want it. The man who bought it doesn't need it. The man who needs it doesn't know it. What is it?

A coffin
A tombstone
A funeral

I'm thinking something in that area...?
If not, then 99.9% of 21st Century consumer products.

Yes it does and seeing how we've all googled it already I'm going to state it so we can move on
Shadow

a Splinter?

unless it's something from the eletro-magnetic spectrum, it will have mass, and therefore weight.
if it's not light, the riddle is scientifically false

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

A hole.

to make a hole, you have to remove something from the bucket, the riddle says PUTTING something in a bucket.
though we use the language in the riddle for everyday speech, it is not technically correct.

not anymore

and how the hell did you manage to outlike me?

cause ya'll cooking sucks

A last name?

You are correct! Here's another one

The paragraph below is very unusual. How quickly can you find out what is so unusual about it?
"Gatsby was walking back from a visit down in Branton Hill's manufacturing district on a Saturday night. A busy day's traffic had its noisy run; and with not many folks in sight, His Honor got along without having to stop to grasp a hand, or talk; for a mayor out of City Hall is a shining mark for any politician. And so, coming to Broadway, a booming bass drum and sounds of singing, told of a small Salvation Army unit carrying on amidst Broadway's night shopping crowds. Gatsby , walking towards that group, saw a youg girl, back toward him, just finishing a long, soulful oration ... "
The above passage is taken from the book "Gatsby" written by Ernest Vincent Wright in the late 1930s.

I'm going to half-jokingly guess "children".