Why is my mobile hotspot so much slower than my regular data connection?

Well, that would certainly explain it, but is it supposed to be this way? The description of the mobile hotspot in the T-Mobile app itself says it uses the 4G LTE network.

I've had T-mobile service for roughly 15 years. Up until recently my tethering used to be the exact same speed as my phone data speed. No more. Using speedtest.net it's about ½ as fast. Not sure what happened to T-mobile lately, but their service and their customer service has dropped way off. T-mo used to be one of my favorite vendors for personal/work. I was a huge advocate/ambassador for them. But not lately, and it's really disappointing. I can't help but wonder if this new worse service level has anything to do with the Sprint merger. Hope they get their act together soon or I may look elsewhere at my next upgrade.

Hotspot data is throttled down to approximately 3G speeds.

Well, that's frustrating, but thanks for the answer!

T-mobile customer service fucked me around with this . The device hot spot was CLEARLY very quick and reliable months ago. Now it is USELESS! So slow, in fact, that I cannot even load the gmail in under ten minutes on my Chromebook or laptop. The devices are fine on other networks. The phone web service is fast. But the fucking hot spot is ridiculously slow now. 
 

They offered NO solutions other than to try and sell me another plane--with a limited bandwidth of 4g hot spot. So, T-mobile can go  itself in it's . 

I am beyond frustrated with this issue. I've been a TMO customer for 20 years. This issue is unfixable at the client side and hours of calls with support does nothing. There is clearly some network management rule in effect that throttles speeds for users accessing the hotspot feature regardless of what plan you have. It doesn't matter what phone you have, what city you are in, what time of the day it is, what is included in your plan, or how much data you used up to that point.   NEVER delivers 5g speeds or even 4G speeds most of the time. It's significantly slower. Often it's completely unusable (dropping to less than 1Mbps) despite not being close to being over the 40GB cap. In addition, they consistently overstate the hotspot usage in order for you to hit whatever cap you have. 

This issue really sucks and it's affecting my remote work which requires a reliable internet connection and the ability to not have a zoom call that is a choppy, distorted mess. I'm at the point where I really have no choice but to cancel after 20 years and switch to a different service provider. This is my first and potentially last post. I never complained about anything that entire time until now. But I'm tired of paying for a service that doesn't deliver what was advertised and wasting countless hours trying to resolve it. The only fix is for TMO to stop throttling users on the network side whenever hotspot is used. 

It does, just throttled down to slower speeds unless you pay for 4G speeds with Hotspot add-ons.

There shouldn't be any speed reduction unless the data bucket usage that you pay for is depleted. If that's not the case, there may be something else going on with the hostpot connection.

Well, that's two opposite things I'm being told now. Is the mobile hotspot reduced to 3G by default, or should I be getting the same speeds as I see when I use the phone data connection itself??

I have the Simple Choice plan from several years ago. The mobile hotspot description seems to indicate that I have 4G LTE data for it. It says:

"No Wi-Fi available? No worries. Use your device as a mobile hotspot -- backed by the power of T-Mobile's award-winning 4G LTE network."

That's all it says under the "Mobile hotspot" section.