Because air has been introduced into the water supply system. This is caused by the pipes being drained because they were cut and mended. So when they turn the water supply on again air pressure stop water from filling the pipes. (Because pipes are airtight and so are your taps)
To remedy this you need to open cold water tap and let it run. Don't runt your hot water tap because you might introduce dirt into your heating system. You will hear hissing and spewing noise. Once water starts to run let it run for another minute. You might notice muddy water. If you do let it run for another minute or two until the water is clear.
Sometimes taps have filters (aerators) on them and they can get clogged up causing pressure issues. Also if you did run warm water during priming then it is likely that other filters are blocked. You need to find out which ones, clean or replace them now. Most likely a plumber will be needed to find the problem.