The middle class does not have the ability to hide and escape like the rich. Even if the country is full of corruption they have to pay taxes to the government within their limits. Rich people who evade income tax don't show it even if they have money in the bank And for this a class of officers of Bank and NBR help them in exchange of benefits and they keep a part of their income outside the banking channel and smuggle it out of the country.
Middle class is getting lower and lower in number. What we used to consider middle class was the family that had one father working, mother taking care of the house and the kids, kids going to school without debt, they had one house, one car they changed every 5 to 10 years, and one vacation every summer. Nowadays what we consider as middle class are the people who have debt lower than 3 months worth of salary, that is true if you have debt lower than your 3 month salary then you are a middle class.
Most have no homes, barely a car that runs, school debt even in your 40's, and many more trouble as well. This means that as long as we keep this trend going, we are going to have middle class at "if you have a job then you are a middle class" level eventually.
No, not getting lower in number but getting higher in number actually according to their new definition because it's easy to have a debt and other negative things that you mentioned there. I still think that this is not totally their fault but it can also be because of the recession, etc... , most especially inflation and its continuously increasing rates.
Sorry to say this but I think the governments, banks, and the likes, can also be the reason on why it happens. Having a job is already one of the qualifications for being a middle class. Maybe you can instead say that having no job will soon still be considered as it. They (lower class, middle class, and so on...) are mainly just a term anyway, and I think there is no real big deal on them whichever or whatever you define them.