The production of weak blocks occurs randomly as miners work towards achieving a full-PoW block. The integrity of these blocks directly reflects the transactions miners aim to include at the time of creation. If a weak block were to include an invalid transaction, it could risk being upgraded to a full-PoW block with the same invalid transaction, leading to rejection by the network and loss of block rewards. Consequently, miners might opt not to broadcast weak blocks to conceal their transaction strategies.