Celebration before Game end

[potato]

I notice when the lead is too much, players tend to give up the last 10 seconds and start shaking each other's hand, and when it's the finals coaches & bench players etc will start walking into the court before the buzzer hits, yet no calls were called for such violations. I know it bears no meaning to the game but rules are rules, aren't such action considered serious and both teams should be called for technical fouls?