If you are painting cabinets that have never been installed or varnished you could paint without sanding however, we NEVER do that!
If there is any sign of food, oil from your hands, build up of grease near handles and pulls in corners etc... you need to completely remove grease and the best way to do that is SANDING. If you don’t sand... paint will always chip or peel the moment you clean or hit those areas. Cleaning and sanding is the MOST IMPORTANT step to kitchen cabinet painting and refinishing.
Products like degreasers or TSP never work for older cabinets. If they actually worked we would be millionaires. In fact we never use TSP