In my opinion it's "advertising"; To the doubters; To their own people seeing friends not come back that the sacrifice is worth it; To the EU showing the damage to Russia; To other countries interested in buying some capability.

If you never advertise your wins, people think your just getting rolled.

Edited for formatting.

My guess:

It shows an deep penetration and destruction of Russian defenses. They don't really give too many specifics on how they did it but what they accomplished.

Russia would prefer not to broadcast how Ukraine was able to hit them this hard. The leadership likely already has reports of how bad of a screw up this is on their side.

Ukraine needs all the positive news from the war it can get for both internal motivation/recruitment and external funding/resource procurement.