avia post navigation on mobile

is there a special reason for setting the post navigation to display none on screens under 768px ?

i have set up the media query to the following and it looks for me ok on my iphone ( i shrinked a little bit for that case

@media only screen and (max-width: 767px) {
.responsive #top .avia-post-nav { display: block }
#top .avia-post-next {background:none repeat scroll 0 0 rgba(255,50,50,0.6);top: 65%}
#top .avia-post-prev {background:none repeat scroll 0 0 rgba(50, 100, 255,0.6);top: 65%}
#top .avia-post-nav {height: 60px;margin-top: -55px;padding: 15px}
.avia-post-nav .entry-info-wrap {margin-top: -11px}
.avia-post-nav .entry-info {height: 50px;width: 180px}
.avia-post-nav .entry-image {height: 50px;width: 50px}
.avia-post-nav .entry-info span {display: table-cell;font-size: 13px;line-height: 1.3em;vertical-align: middle}
.avia-post-nav .entry-image img {display: block;height: auto;width: 50px}
.avia-post-nav:hover .entry-info-wrap {width: 200px}
}