*If* you're making a call, the landline might- but that's not the point.
If an individual leaves the house with their cell phone and goes on an
outing, the amount of information they have provided to their local
telecommunications company is staggering. Firstly, the location metadata. Not
literally pin-pointing an individual doesn't make this weaker:
http://www.abc.net.au/news/2015-08-24/metadata-what-you-found-will-ockenden/6703626
Then, if a modem rootkit is available, anything from audio recordings to gyro
or whatnot data- which may very well be sufficient to determine what you type
on a keyboard- become available, even if you haven't decided to take a single
call. With a landline, by contrast, the most that can be determined is
whether or not you have taken any calls placed through, and whether or not
you placed any calls: much more reasonable.
Of course, the mobile's disadvantage is somewhat the cost of being able to
connect whilst moving. However, apart from the obvious fact that this doesn't
make it any less surveilling, the network could likely be done slightly
better.