I have set Default value for a Picklist, but to my luck it is not working, don't know the reason for the same.

Can anyone help me with any workaround? Even Custom Picklists are not working with default values on Account. Although it is working for Contact. 

Default Value:

New Account Page:

 

trigger NumberOfContacts on Account (before insert, before update) {
    if(trigger.isinsert)
        for(account a:trigger.new)
            a.Number_of_contacts__c = 0;
    else
        for(account a:[select id,(select id from contacts) from account where id in :trigger.new])
            trigger.newmap.get(a.id).Number_of_contacts__c = a.contacts.size();
            
        for(account b:[select id,(select id from contacts where Inactive__c = False) from account where id in :trigger.new])
            trigger.newmap.get(b.id).Number_of_active_contacts__c = b.contacts.size();
}