No, it is not illegal to not use a washing machine. Using a washing machine is a matter of personal preference and convenience. There is no law or regulation that requires individuals to use a washing machine for their laundry needs.
People have been washing clothes by hand for centuries before washing machines became widely available. While washing machines offer convenience and efficiency, some individuals may choose not to use them for various reasons, such as environmental concerns, water conservation, or personal preferences.
It's essential to note that some rental agreements or housing associations might have rules or guidelines regarding the use of washing machines in their properties, but this is a matter of contract or community policies, not a legal requirement.
Ultimately, how you choose to wash your clothes is entirely up to you, and as long as you follow any applicable rules or agreements within your living arrangement, you are free to use or not use a washing machine as you see fit.