"Borrowing" melodies from other songs

[system_09]

So anyway maybe It's just me but I noticed that a lot of melodies in pop music are borrowed from other well known songs.
I dont know if this is done intentionally or no (probably sometimes both) or maybe I am just over analysing while I listen, but I cant help but notice.
May this be one of the reasons that it all usually sounds so familiar yet new?

I have some examples actually ( not a lot I can find off the top of my head but still)

Kesha - Take it off
https://www.youtube.com/watch?v=JQDXe4xl2zA&list=PL2132B238C8D53C9F
The very first melody (and the melody of the chorus) is the melody usually used in cartoons when snake charmers play. Maybe you remember

Jonas Blue - Perfect Strangers
https://youtu.be/Ey_hgKCCYU4?t=1m15s and
https://youtu.be/zeBDoNBNMro?t=37s Mas Que Nada
Actually when I only heard the chorus it reminded me of this song, really familiar

Taylor Swift - Clean
https://youtu.be/o2Hfiujc_1c?t=1m16s
https://youtu.be/xwjwCFZpdns?t=33s Hailee Steinfeld, Grey - Starving ft. Zedd
Well the chorus from Taylor Swift and the hook from the second track are just identical

Taylor Swift - style
https://youtu.be/-CmadmM5cOk?t=3m11s
https://youtu.be/PIb6AZdTr-A?t=1m6s Girls wanna have fun
The melody is also quite similar

Now, I'm not saying that the songs are stolen, I'm just saying the new songs usually have a lot of motifs from old songs in them that make them feel similar.
Some will probably think this is rubbish but, maybe you also noticed some songs that borrow motifs/melodies/phrases from other songs?

What are your thoughts about this?

[heyheyhey]

Shellback's drums at the beginning of taylor swift - "shake it off" always remind me of the beginning of The Ting Tings - "That's Not My Name" ( http://www.vevo.com/watch/the-ting-tings/Thats-Not-My-Name/GB1100800083 )

[bugmenot]

it's a up and down scale, not a melody.
simple scales or a repetition of one note are easier to sing, it's more catchy, it's everywhere.
do you play musical instrument?

Kesha - Take it off
3-4-5-4-3
3-4-5-7-5-4-3

Perfect Strangers
7-6-5-4-3
4-5-4-3

Mas Que Nada
7-6-5-8
7-6
7-6
7-6-5-8

Style and Girls wanna have fun
5-4-3-2-1

Clean and Starving are not similar, just zig-zag kind of a melody

[j.fco.morales]

I agree, is rhythm. Not melody.

[system_09]

Well yeah, you can change a couple of notes while the rhythm remains the same and it becomes a new melody.
I'm just saying that a lot of material is reused in pop music, for example the song

The Weeknd - Rockin'
and
Ellie Goulding - Keep On Dancing

The first phrase in both songs sounds very similar. The Weeknd's song is written by Max Martin. And it actually sounds that if it wasn't for the weeknd, the song would fit perfectly for Ellie Goulding. Even the chorus sounds like in her style of singing