Why is snap packages shown in lsblk output?

I recently installed a ubuntu-core snap package. And this is the output of lsblk

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    1  14.9G  0 disk 
├─sda1   8:1    1   1.9G  0 part [SWAP]
└─sda2   8:2    1    13G  0 part /
sdb      8:16   0 149.1G  0 disk 
├─sdb1   8:17   0   100M  0 part 
├─sdb2   8:18   0  59.9G  0 part 
└─sdb3   8:19   0    62G  0 part 
sr0     11:0    1  1024M  0 rom  
loop0    7:0    0  64.7M  0 loop /snap/ubuntu-core/109

Is this shown because each snap is sandboxed??

Each snap (in 16, not in 15.04) is a squashfs file which, when installed, is mounted.

lsblk shows volume information for all mounted file systems. Because that one particular volume is still mounted it shows up in the lsblk output.