Nice is holding the door for the person behind you as you walk through it. It’s giving someone a bouquet of flowers just because you feel like it. Or, checking up on friends every once in a while to see if they’re okay.
Why would nice be wrong?
When it comes to being nice, there’s no so that’s.
Being nice isn’t gifting somebody a box of chocolates so that you can consider it a rain check for a future favour. It’s not texting your colleague a “How are you?” so that you can ask them to buy your branded merch. It’s not talking up somebody so that they’ll like you and give you free gifts in return.
When it comes to being genuinely nice towards others, there shouldn’t be expectations for returns (otherwise it wouldn’t actually be nice).