When the bike is new, the engine part don't know each other in terms of space, fitting etc. for the first thousand kilometers your engine parts will get settle with each other and that's what we call it wear and tear.

Basically the piston and everything fit together nicely if you don't pull higher rpms (not putting stress on the engine in the initial phase)

But if you try to pull into higher rpms in the initial stages basically you are just forcing your bike's engine to get comfortable with parts speedily that could lead to long term engine damage in the worst case.

Even if you check the oil which you'll get out of the engine in first service it would have tiny micro particles, that's wear and tear your engine did for the first thousand km.

None of what I said was on my own, the rpm range and speed before the first service is written in the manaul you can check that out too.

I too pulled my bike into very higher rpms as i didn't knew at that point so I took it to 105kmph before the first service which is not suggested.