if the channel is economically productive there is little incentive for the lsp to close it. if the channel is dormant then capital allocation is very poor if you don't close the channels after the duration for which you were paid for (1y in this case). Of course there is also the opportunity cost of closing the channel - will the onchain fees be higher than potential revenue from capital reallocation

another thing to consider is that users go away so you don't really want to keep the channels who are not doing any traffic since its also a high possibility that the user stopped using the wallet/lost keys/forgot about it. but this goes back to the efficiency of capital allocation from before.