Those nurses don't need to interrogate you. You can always say "well, I have many friends at other clinics, and yours is the only one who does not check. It concerned me". It's true, and then the nurses will lay off interrogating you as to what you want to know, which they should know themselves anyway. They are probably not even nurses, just techs.
I would insist. Yes, you are right, they check to make sure levels are looking good to sustain early pregnancy. For myself, I did have a problem and needed extra estrogen when using my own eggs. The clinic always did B/W day of transfer and a few days after transfer.
For DE, I also have had BW checked day of transfer and a bit after transfer before BETA, but I never needed supplementation. Maybe they think if the embies are good, they will attach and you should have good levels if the pregnancy is going to stick.
I am not trying to worry you, I am sure you will be alright, it just peeves me that anyone would make you feel like you should not ask for these things. It's your cycle and your money.