Is there any disadvantage of apply default constraints over every fields of DB table

I basically agree. But why taking care of performance, if the logic and the functionality can endangered? Please see my other comment below.
—SA

The question does not really make sense, because of one apparent reason: to discuss "advantages" or "disadvantages", you have to describe two or more alternatives? What alternatives do you suggest to consider? I don't know. If your application's semantic involves some non-default constraints, which is more than likely, do you think you have a choice? Or do you want to carry the constraints out of the database schema and implement them in some application programs (remember, you might have more than on over the same database), ask yourself: how these rules can be data-driven? If they are not, it would be a really bad idea. Especially if you have more than one application program. Imagine the situation: one application can populate some data which is not valid from the standpoint of another application. Do you think it can be acceptable?
—SA
—SA

Ask yourself "why do I need a default constraint?".

The reason to a default value for a field is that you wish to, at times, omit entering a value in a field when you insert a new record and NULL (the default default) is unacceptable.

Per Sergey, above, you have to be aware of what will now (and may in the future) access the table.

Some fields, on the other hand, beg a default constraint, such as the creation time of a record. Although I use this commonly, it is rare, indeed, that I put in any other default values for a field. You can always handle NULL in your queries and thus avoid the risk of unintended consequences down the line.