India and Africa have a lot of track that has been laid in the old-fashioned way, with short lengths of track used and with expansion gaps deliberately left between them. (It was the existence of those gaps that resulted in the 'clickety-clack' sound of trains passing over the tracks in John Betjeman's days).
Such track-laying techniques cost vastly more in labour, not only when the tracks are laid but forever after in order to keep the track in good condition (especially when high-speed running is required).
The use of continuous track cuts down costs (both in track-laying and in subsequent maintenance), greatly improves safety (because there's no chance of a single section of track becoming misaligned, leading to a possible train derailment) and permits higher running speeds. The only slight disadvantage is that running speeds have to be reduced in hot weather but, even then, they'll probably be no slower than the maximum that would have been possible using the older track-laying technique.