I can’t say for sure what’s going on here, but as much as I hate to blame your equipment, I think that the reason you’re not hearing the bass much is because your speakers aren’t reproducing the bass frequencies fully. Even if the guitar is sounding rich and full on a given set of speakers, that doesn’t mean that they’ll be able to pump out low frequencies, and the standup bass is mostly low frequencies.
On my larger Bluetooth speakers, my AirPods, and my studio monitors, the bass is prominent and lifelike. But on other speakers, such as smaller Bluetooth speakers or built-in device speakers, the bass isn’t nearly as audible because bass frequencies in general aren’t as audible. I don’t know any way around this. I think commercial tracks sometimes use tricks to make it seem like there’s more bass audible then there is, but I’m not sure I could make use of those in an app setting and anyway I like to “keep things real” as much as possible when it comes to the audio.
One test you could try is to connect your phone or iPad to your car’s speaker system, if your car supports Bluetooth. Car speakers often have a pretty good bass response, although this isn’t true across the board. I know some folks who practice in the car (with Strum Machine) because that’s where they can get the best sound.
Another thing you could do is test your speakers with a YouTube video (like this one) where I can confirm the bass is nice and audible. If you can’t hear it on a device, that means the device is having trouble with those lower frequencies.
What model of Bluetooth speaker are you using? Perhaps I can look up the specs and make a more educated guess as to whether that’s the culprit or not.