Are fiscal rules necessary in a currency area?

Are fiscal rules inevitable in a currency area, or can a currency area get by without them? When the euro was created, it was thought that fiscal rules were needed , because if a country had an excessive fiscal deficit, the currency area’s common interest rate would rise. But it is now known that fiscal deficits do not give rise to this negative externality; One might think on the contrary that there is market discipline: if a country has an excessive fiscal deficit, its sovereign risk premium rises, which encourages it to correct its fiscal deficit. Market discipline would thus absolve the need for fiscal rules; But the problem is that if the country does not react to market discipline, or if it reacts too late, it ends up engulfed in a public debt crisis, especially if the market discipline acts late and drastically, forcing the other countries of the currency area to bail it out. So fiscal deficits do have a negative externality if they are highly excessive and if market discipline is insufficient to get the country to correct them , or if it acts too late and drastic ally . We see that fiscal rules are needed in a currency area simply to avoid crisis situations, and not just excessive fiscal deficits, which are corrected by market discipline.