This way of thinking is strange and evil.
We should use reward mechanism to motivate users, not punishment system to govern customers, although sometimes the difference between the two is not significant.
The problem you mentioned can be solved by greatly increasing the power of the combined card. It is a strange thing that there is no reward for the combined card.
You will be rewarded if you merge, not punished if you don't merge.
It does reward and motivate users. It motivates them to both level up and to combine and hold on to their cards in order to reach higher rewards. You have to understand that any game like this including hearth stone etc all require continued investments to build your decks. Look at Pokémon players and other card game players they constantly are buying. If no one is buying and there's no demand and everyone just gets everything for free then value just gets sucked out and never replenished. People need to stop thinking crypto and money is printed and handed out. That's not a sustainable system.