Because of how halving works to prolong the "original" mining phase.
Like many altcoins, Joulecoin implements the halving technique to more slowly reach the total supply of issued coins (~ 45 million XJO).
We are currently in our second halving stage which results in a XJO reward of 4 instead of 8 or 16.

According to Joulecoin configuration, halving occurs every 2 years.

So, roughly 2 * (31 556 926 / 45) approx. 1 402 530 (this means that approximately block 1 402 530 should have the new block-award since 2 years have passed, but if the chain have had issues this could be longer or shorter)

If we look at Block explorer at around 1 400 000 (https://chainz.cryptoid.info/xjo/block.dws?000000000000f6256c21d60466bc9b7aab1704f5681e504546d1e9ca48074d9e.htm)
We can see that there still is the original 16 XJO reward.

So, let's calculate where 4 XJO happens. (4 * (31 556 926 / 45) approx. 2 805 060)

If we look at Block explorer again, but at 2 800 000 (https://chainz.cryptoid.info/xjo/block.dws?0000000000001561b85d4dde5aa9ada2fc491fbb1cee8fca9148df0f3e2d48b7.htm)
We can see that the 8 XJO reward is currently in place.

But if we check at block 2 805 060 (https://chainz.cryptoid.info/xjo/block.dws?0000000000000b807131df697a91d769f950b0aa04b4cd6cc09d7c50928d929b.htm)
We can confirm that the 4 XJO reward have indeed started occurring.

Disclaimer: I know this math is not preferred*