Due to lower frequencies, L-Band is easiest to implement for mobile systems. Inmarsat provides in L-Band the most well know service in this frequency band.
There is absolutely not much L-Band bandwidth available. The spectrum is very rare.
The higher you go in frequency, the more bandwidth is available, but the equipment needs to be more sophisticated and easily can get affected by RF antenne geometry damage.
If one could equate the cost and availability of L-Band space segment to say, the Rolls Royce, C-Band might be theMercedes. Ku band the Volkswagen, and Ka-Band the Smart.
Being a relatively low frequency, L-band is easier to process, requiring less sophisticated and less expensive RF equipment, and due to a wider beam width, the pointing accuracy of the antenna does not have to be as accurate as the higher bands.
Only a small frequency slot (1.3-1.7GHz) of L-Band is allocated to satellite communications on Inmarsat.
Inmarsat uses L-band for their Fleet Broadband, Inmarsat-B and C.
The older Inmarsat A and B antennas were typically 1 meter in diameter, but, with the launch of more powerful satellites and the use of steerable spot beams, the new fleet broadband antennas are down to less than 30cm.
L-Band is also used for low earth orbit satellites, military satellites, and terrestrial wireless connections like GSM mobile phones.
Since there is not much bandwidth available in L-band, it is very expensive.