Many a times employers/managers want employees to work on weekends or longer hours per day. Is it fair? This has no concrete answer as yes or no. If you are someone who is watching work hours more than productivity, it is likely that you want your team to put extra hours at office even without major task delivery.
If reaching the deadline is your main concern then yes asking for extra hours makes sense. But if you are making it as a regular practice you may need to review your strategies again. May be something unwarranted is consuming more time like status calls or meetings, or you are going wrong in project work and time estimation, or you give a lazy start and demand to cover up at the end. For sure if you make it a routine to come to office on weekends, most of the folks will not be willing to do so. But just that boss is boss, your wish is being treated as command!
If there were unexpected pot-holes and unexpected amount of time got consumed to fill them up, it is absolutely fair to ask team for extra hours. But how do you make that as a willingness and not just as an order? As a founder or person behind the idea you might want everyone in the team to have the same passion and spirit as you have. It will not come naturally though. Keep the team motivated and energetic. Your own enthusiasm towards work and efforts for it will be capable of injecting the same spirit in others. Value their inputs, suggestions. Appreciate their performance.....that gives you the right to express your unhappiness for a poorly performed task too. Everyone should be given the feeling of being equally important and indispensable for the project. Happy employees = productive employees (true most of the times).Team members should have the feeling that you view each and everyone under the same lens and no favoritism is being shown towards anyone.
You getting your team members involved more on all the fronts of project will help to feel the ownership. In many startups employees don't feel job security or delayed salaries form a major concern. Such insecurity naturally keeps them in the quiet loop of being in hunt for a better job. Such hurdles can be overcome by sharing updates like what all projects have been signed off and what is expected in pipeline. Of course you should be not be far away from ground reality!
Ultimately it is the feeling of loyalty towards you and the work that your team will go beyond the call of duty to help you out.