if you do not stake the USDT you have then the value of the assets you own in the coming year remains at $1k because the USDT value does not change. with stake the amount of USDT you have in the coming year will increase from 1000 to 1095. people who do this are risk averse because stakes other than stable coins have the risk of decreasing the price of the coin.
I agree, it will remain the same if he will not stake it but if he do there's a small to big changes will happen in the total amount he stake. Staking is better if the amount you are holding is big and the apy looks promising, but the cons in some coin is the price might go deeper depending to the market situation.
The very purpose of doing your research, but if you are a conservative type of investors,
Staking stable coin and gaining a small amount of stake rewards but very passive is the first thing that you have in mind,
there are people who know how to play with this kind of investment, some are risk takers who choose to invest and
stake with crypto and see if luck will bring them huge amount of stake benefits.