Event loop delay

I have this simple code in NodeJs

const { eventLoopUtilization } = require('perf_hooks').performance;
const { monitorEventLoopDelay } = require('perf_hooks');

const h = monitorEventLoopDelay({ resolution: 10 });
let lastELU = eventLoopUtilization();

setInterval(() => {
  console.log('Start', new Date())

  const tmp = eventLoopUtilization();
  console.log(eventLoopUtilization(tmp, lastELU));
  lastELU = tmp;

  console.log(h.min);
  console.log(h.max);
  console.log(h.mean);
  console.log(`End ${new Date()} \n\n`)
}, 1);

h.enable();

When I execute this I have this output:

...

Start 2024-07-18T14:20:49.400Z
{
  idle: 14.759,
  active: 0.2114000018537041,
  utilization: 0.01412119928843101
}
15417344
16138239
15742566.4
End Thu Jul 18 2024 16:20:49 GMT+0200 (Central European Summer Time) 


Start 2024-07-18T14:20:49.415Z
{
  idle: 15.022599999999997,
  active: 0.29309999828934963,
  utilization: 0.019137225090729564
}
15171584
16138239
15648085.333333334
End Thu Jul 18 2024 16:20:49 GMT+0200 (Central European Summer Time) 

...

As you can see, every loop of the event loop is taking ~15ms to complete.
That's causing every callback to "lag" 15ms on average.

The event loop utilization show that almost all 15ms of the time is idle.
I cannot understand why.

Someone has an explanation?
Thanks