I know that the question is quite stupid but I want to get an insight of this case. consider 3 resistors connected in series with a battery, after the current passes through resistor 1 it loses some of its energy, the kinetic energy of the charge carriers will definitely also decrease and so does the drift velocity then why doesn't the current decrease? Its quite confusing.
Current is due to the drift velocity of electrons . In the Transient State when the current sets up there is an accumulation of electrons at places like bends in the wire. There is an electric field ( small) in the wire that drives the current. At any place where there is an accumulation of charges the outflowing current will be less than the inflowing current and the field will act in such a way so as to equalize the current. It so happens at the ends of the resistor. But all this happens in such a quick time that for all practical purposes the current is same in every brach of the circuit.
It is just like the electrons which have reached the end of the first resistor communicate the presence of the resistor to the electrons coming behind them and convey them that they have to come slowly because there is a resistor ahead.
Griffith explains this very efficiently. Also there a certain beautiful answers here concerning these questionS !
You are right - but not for long...
The situation you describe is unstable. This is not steady current. More electrons enter the resistor than what leave it. It will be "filled up" quickly. There will be a pile-up, a queue, of incoming electrons waiting to enter.
When electrons accumulate at a point like that, the electric field increases there. This will repel new arriving electrons more and more. Less electrons then show up.
The current before the resistor is reduced because the current after is smaller.
In the end it equalizes, so that just as much enter as what leaves per second. And the current is then constant and equal on either side; it is steady.
The question is worded ambiguously. It could be construed to mean why isn't the current less in each additional resistor than it was in the resistor before it. The answers already here answer that question.
The question could also be asking why isn't the current less when it flows through 3 resistors in series than when it flows through one. If we assume that all the resistors are equal, then the current is reduced by each additional resistor added to the circuit. In fact you would have only one-third as much current flowing through three of the resistors in series as you would have flowing through just one of the resistors. So the current is reduced by each additional resistor, but except for things that happen over very short timespans, each resistor will always have the same current flowing through it as any of the other resistors.